Abstract
Introduction
Alopecia is a common hair loss condition with different treatment modalities. Platelet-rich plasma (PRP), a minimally invasive autologous therapy, has emerged as a topic of interest, but its effectiveness remains debated. The present systematic review and meta-analysis aims to evaluate the safety and efficacy of PRP for alopecia.
Methods
A comprehensive search of PubMed, EMBASE, and Scopus conducted on 27 May 2025 with monthly updates until July 10 2025 identified 43 randomized controlled trials (1877 participants) assessing PRP in alopecia. Primary outcomes were changes in hair density and thickness. Secondary outcomes included side effects, hair loss, clinical improvement, patient satisfaction, recurrence, and other hair follicle metrics.
Results
Activated PRP was effective in increasing hair density and minimizing recurrence compared with placebo, whereas non-activated PRP was associated with a higher frequency of adverse effects. PRP also improved clinical outcomes and patient satisfaction. Moreover, hair loss decreased with PRP therapy regardless of activation status or control type. However, PRP did not significantly affect hair thickness. However, PRP did not significantly affect hair thickness.
Discussion
These findings support PRP as a relatively safe and effective therapy for alopecia, particularly in increasing hair density and reducing hair loss. Patient satisfaction was generally favorable. The clinical efficacy of PRP was often comparable or superior to conventional treatments. Activation status appears to influence response, highlighting the importance of preparation protocols. However, as a result of heterogeneity in study designs and incomplete reporting of the effect of specific PRP composition-related covariates on treatment efficacy or patient safety outcomes, no significant variation in overall effect modification was attributable to alopecia subtype.
Conclusions
Moderate evidence highlights that PRP is safe and effective in improving hair density, reducing hair loss, and enhancing clinical outcomes and satisfaction. No significant benefits were demonstrated for hair thickness or other follicle-related parameters as derived from PRP therapy. Further high-quality, standardized trials are needed to confirm these findings and clarify the clinical significance of PRP formulations.
Supplementary Information
The online version contains supplementary material available at 10.1007/s13555-025-01542-8.
Keywords: Platelet-rich plasma, Alopecia, Hair loss, Hair density, Systematic review, Meta-analysis
Key Summary Points
| Why carry out this study? |
| Alopecia is a common condition with limited consistently effective treatments, creating an unmet clinical need for safe and efficient therapies. |
| Platelet-rich plasma (PRP) has emerged as a minimally invasive, autologous option, but its efficacy and safety remain uncertain. This systematic review and meta-analysis aimed to evaluate the safety and effectiveness of PRP in improving hair parameters and patient outcomes in alopecia. |
| What was learned from the study? |
| Patients treated with activated PRP significantly increased hair density when compared with placebo and showed a lower recurrence rate. |
| PRP administration increased patient satisfaction, reduced hair loss and the proportion of telogen hairs overall, whereas both clinical improvement and the proportion of anagen hairs were enhanced when compared with placebo. |
| PRP appears to be a moderately effective and safe treatment across diverse etiologies of hair loss, particularly when activated, with clinical outcomes comparable or superior to conventional therapies. |
Introduction
Alopecia—characterized by the progressive hair loss—is a prevalent condition that affects a significant proportion of the global population [1]. This group of dermatological disorders is primarily classified into two subtypes based on follicular integrity: cicatricial alopecias (CA) and non-cicatricial alopecias (NCA) [2]. Cicatricial alopecia is characterized by progressive follicular destruction, in which follicules are replaced by fibrotic structures, leading to irreversible hair loss. This subgroup encompasses various distinct clinical entities, including lichen planopilaris, discoid lupus erythematosus, central centrifugal cicatricial alopecia, and folliculitis decalvans, each characterized by specific inflammatory patterns and pathophysiological mechanisms [3, 4]. In contrast, non-cicatricial alopecia is defined by hair shedding without permanent follicle destruction, preserving the potential for hair regrowth. Common types of NCA include androgenetic alopecia, which is hormonally mediated and genetically influenced; alopecia areata, an autoimmune condition characterized by patchy hair loss; and telogen effluvium, a reactive condition triggered by physiological or emotional stressors [5, 6].
Alopecia can have a significant negative impact on quality of life, leading to considerable psychological distress, negatively impacting self-esteem and overall quality of life [7]. Despite the range of therapeutic options available, including pharmacological treatments and surgical interventions, many patients turn to alternative, minimally invasive treatments that provide a lower risk of complications and fewer side effects [8]. Among these options, platelet-rich plasma (PRP) has been progressively highlighted as a potential therapy for the treatment of different forms of hair loss, including androgenetic alopecia, alopecia areata, and telogen effluvium [9]. PRP is an autologous blood derivative enriched with a platelet concentration above that normally contained in whole blood. Platelet α-granules promote the release of various growth factors, cytokines, and other biomolecules, including vascular endothelial growth factor (VEGF), platelet-derived growth factor (PDGF), epidermal growth factor (EGF), insulin-like growth factor (IGF), fibroblast growth factor (FGF), and transforming growth factor beta (TGFβ) [10, 11]. These bioactive molecules are known to promote cellular proliferation, migration, angiogenesis, and tissue regeneration [12].
When administered via intradermal injections into the scalp, PRP is hypothesized to stimulate dormant hair follicles, enhance microcirculation, and induce promotion of anagen phase, thus potentially improving hair density and regrowth [13]. While the clinical adoption of PRP application in the management of hair loss has become widespread, the scientific evidence supporting its efficacy remains inconclusive. Although some studies report promising results in terms of increased hair density and follicular activity, other investigations demonstrate limited or no significant improvements. Inter-study variability may be attributed to several factors, including differences in PRP preparation protocols, treatment regimens, and study populations, as well as methodological disparities across clinical studies [14]. This systematic review aims to synthesize the scientific evidence and critically assess the existing body of literature on the effects of PRP in managing hair loss. By integrating data from randomized controlled studies, this review aims to critically address the evaluation of the clinical efficacy, optimal treatment parameters, and safety profile of PRP therapy for alopecia. Furthermore, this analysis will highlight the gaps in the current evidence base and suggest potential directions for future research.
Methods
The methodology for this systematic review and aggregate data meta-analysis was detailed in a protocol registered with the PROSPERO International Prospective Register of Systematic Reviews (CRD420251047031) on 22 May 2025. The manuscript was structured in accordance with the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols (PRISMA-P) guidelines [15].
Search Strategy
A comprehensive literature search was conducted to identify controlled clinical trials on the use of either PRP alone or in combination with other drug products containing active and/or inactive pharmaceutical ingredients for the treatment of hair loss, without any restrictions regarding type of PRP, causes of hair loss, type of alopecia, administration route of therapeutic agents, dosing regimen, or study population. The computer-assisted search, with no limitations on language, date, or publication status, was conducted using PubMed, EMBASE and SCOPUS on 27 May 2025 with monthly updates until July 10 2025 using a combination of the following terms to optimize both search specificity and sensitivity: alopecia, androgenetic alopecia, AGA, FAGA, alopecia areata, AA, alopecia totalis, traction alopecia, scarring alopecia, nonscarring alopecia, non-scarring alopecia, cicatricial alopecia, CA, primary cicatricial alopecia, PCA, secondary cicatricial alopecia, SCA, noncicatricial alopecia, NCA, non-cicatricial alopecia, diffuse alopecia, frontal fibrosing alopecia, FFA, fibrosing alopecia, alopecia mucinosa, telogen effluvium, anagen effluvium, pattern hair loss, diffuse hair loss, hair loss, loss of hair, baldness, lichen planopilaris, LPP, folliculitis, folliculitis decalvans, dissecting cellulitis, folliculitis keloidalis, folliculitis necrotica, erosive pustular dermatosis, Graham Little syndrome, classic pseudopelade, central centrifugal cicatricial alopecia, CCCA, chemotherapy-induced alopecia, discoid lupus erythematosus, chronic cutaneous lupus erythematosus, platelet-rich plasma, PRP, platelet rich plasma, plasma rich in growth factors, PRGF, pure platelet-rich plasma, pure platelet rich plasma, P-PRP, leukocyte-poor platelet-rich plasma, leukocyte-poor platelet rich plasma, LP-PRP, leukocyte-rich platelet-rich plasma, leukocyte-rich platelet rich plasma, L-PRP, LR-PRP, platelet-rich plasma gel, platelet rich plasma gel, platelet-rich plasma gel matrix, platelet gel, PRP gel, P-PRP gel, L-PRP gel, and PRP-GM. A detailed description of the systematic search carried out in the different databases is included as Supplementary Material. Additionally, we reviewed the reference lists of the most relevant studies to identify potentially eligible studies that were not captured in the initial literature search. Before screening, a de-duplication step was conducted using combination of automated and manual approaches to remove duplicate citations [16].
Study Selection and Inclusion Criteria
As recommended by Waffenschmidt et al. [17], the list of studies was independently assessed by two reviewers (RT and MH) following a conventional double-screening process, with disagreements resolved via discussion and on the basis of the feedback of a third reviewer (EA). Eligibility was initially determined by reviewing the title or abstract, and the full text was examined if necessary. Articles were deemed eligible if they mentioned the use of PRP for alopecia in either the title or abstract. Studies focusing on any form of human hair loss, including cicatricial alopecias and non-cicatricial alopecias, were included. This review considered only full-text randomized controlled clinical studies published in English, including split-head and other self-controlled experimental designs, regardless of the control treatment type (including placebo, active control excluding PRP across different administration regimens or the absence of treatment). The focus was on treatments for hair loss in which PRP was administered either as a sole therapy or as primary or adjuvant treatment for hair loss regardless of experimental design, PRP composition and delivery method, frequency and routes of administration, disease status, etiology, specific symptoms or patient-related characteristics. Preclinical in vitro and/or in vivo studies, case reports, case series, uncontrolled observational studies, uncontrolled prospective studies, retrospective studies, narrative reviews, scoping reviews, and systematic reviews (with or without meta-analysis) were also excluded.
Population
Individuals experiencing temporary or permanent hair loss regardless of their age, gender, ethnicity, or health status were included in the selected studies. All types of cicatricial and non-cicatricial alopecia were considered eligible, including androgenetic alopecia (AGA), fibrosing alopecia (FA), alopecia areata (AA), alopecia mucinosa, alopecia totalis, telogen effluvium, anagen effluvium, pattern hair loss, diffuse hair loss, lichen planopilaris, folliculitis, Graham Little syndrome, dissecting cellulitis, erosive pustular dermatosis, classic pseudopelade, central centrifugal cicatricial alopecia (CCCA), discoid lupus erythematosus, and chronic cutaneous lupus erythematosus.
Interventions
Injected PRP formulations, either alone or in combination with other therapeutic agents (e.g., corticosteroids or minoxidil), were compared with different injected control treatments, including placebo (saline), corticosteroids, finasteride, minoxidil, or polynucleotides.
Definition of Outcomes
All studies identified through the literature systematic search were assessed to determine the outcome of hair loss treatment. Primary outcomes included hair density (number of hairs per square centimeter) and hair thickness (also referred to as hair diameter and hair caliber). Indirect hair density metrics were inferred from hair count measurements when the former was not directly reported, conditional on the precise definition of the measurement area. Secondary outcomes were terminal and vellus hair density, hair loss, alopecia severity evaluated via Severity of Alopecia Tool (SALT score), clinical improvement based on investigator’s assessment (proportion of participants classified as improved in reference to alopecia evolution), patient satisfaction (proportion of participants that declared to be satisfied following alopecia therapy), recurrence (proportion of patients experiencing the recurrence of hair loss after a sustained phase of clinical improvement or therapeutic response), and adverse effects (proportion of patients experiencing at least one adverse effect as defined by the authors). Adverse effects included any negative or unintended symptoms, signs, or conditions that appear in participants during the course of the study, such as pain, discomfort, edema, tenderness, itching, erythema, burning, bruising, desquamation, headache, or infection. Where available, the outcome measures were reported across different follow-up periods. Hair loss was assessed via hair pull test and the proportion of individuals with positive tests was considered (the test was considered positive when three or more hairs were easily pulled out). For the quantitative synthesis, any positive improvement—regardless of its magnitude—was classified as improvement, based either on clinical assessment or patient-reported perception.
Data Collection and Synthesis
Two reviewers (RT and MH) independently extracted the following data from each study: first author, year of publication, type of alopecia, intervention group, control groups, population size, mean age, male-to-female ratio, outcome measures, follow-up duration, and main results (Table 1). If required, the corresponding authors were contacted for clarification or obtaining additional information.
Table 1.
Characteristics of the included studies
| Study (year) | Study population (n) | Alopeciaa | Male/female (%) | Age range (years) | Intervention group (n)b | PRP activation | Control group (n)c | Population included in final analyses (n) | Frequency and dosing PRP | Outcomes | Follow-up | Main results |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Trink (2013) [34] | 45 | AA | 44/56 | 18–46 |
ILC (15) PRP (15) |
Ca2+ activated | PBO (15) |
ILC (15) PRP (15) PBO (15) |
1 month | Hair regrowth (SALT score); hair dystrophy; side effects; cell proliferation (Ki-67 evaluation) | 1 year | PRP promoted hair regrowth and reduced hair dystrophy, as well as alleviated burning/itching sensations when compared to TrA or placebo. Ki-67 levels, used as markers for cell proliferation, were significantly higher. No adverse effects were reported during the treatment |
| Cervelli (2014) [35] | 10 | AGA | 100/0 | 22–60 | LR-PRP (10) | Ca2+ activated | PBO (10) |
LR-PRP (10) PBO (10) |
1 month; 0.1 ml/cm2 | Hair count; hair density; terminal hair density; vellus hair density | 6 months | PRP treatment increased the thickness of epidermis and the number of follicles of hair skin. PRP treated areas showed higher hair densities and also higher terminal hair densities than control areas |
| Gentile (2015) [36] | 23 | AGA | 100/0 | 19–63 | LR-PRP (23) | Ca2+ activated | PBO (23) |
LR-PRP (20) PBO (20) |
1 month; 0.1 ml/cm2 | Hair count; hair density; terminal hair density; vellus hair density | 2 years | A significant increase in the mean hair count and terminal hair density for the PRP group |
| Lee (2015) [37] | 40 | AGA | 0/100 | 20–60 | LR-PRP + PDRN (20) | Non-activated | PDRN (20) |
LR-PRP + PDRN (20) PDRN (20) |
1 week; 0.05–0.1 ml/cm2 | Hair count; mean hair thickness | 3 months | Injections of autologous PRP and/or PDRN into the intra-perifollicular area lead to improvements in hair thickness and density in patients with FPHL |
| Alves (2016) [38] | 25 | AGA | 48/52 | 21–62 | LP-PRP (25) | Ca2+ activated | PBO (25) |
LP-PRP (22) PBO (22) |
1 month; 0.15 ml/cm2 | Hair count; hair density; terminal hair density; anagen hair; telogen hair; anagen/telogen ratio | 6 months | PRP demonstrated a positive effect on androgenic alopecia (AGA) and could be considered a beneficial adjunctive therapy for AGA |
| Farid (2016) [39] | 40 | AGA | 23/77 | 20–40 | LR-PRP + MN (20) | Non-activated | MS (20) |
LR-PRP + MN (20) MS (20) |
1 month | Hair count; investigator’s assessment; patient’s assessment; adverse events | 28 weeks | Both treatment modalities were similarly effective in enhancing hair density and improving alopecia grade |
| Mapar (20P significantly increased hair density 16) [40] | 17 | AGA | 100/0 | 25–45 | LP-PRP (17) | Ca2+ activated | PBO (17) |
LP-PRP (17) PBO (17) |
1 month; 0.1 ml/cm2 | Terminal and vellus hairs | 6 months | RP is not considered an effective treatment option for advanced stages of AGA in men |
| Puig (2016) [41] | 26 | AGA | 0/100 | – | LP-PRP (15) | Non-activated | PBO (11) |
LP-PRP (15) PBO (11) |
Once | Hair count; hair mass index; patient’s satisfaction | 26 weeks | PRP failed to show any statistically significant improvement in hair mass or hair count in women with congenital female pattern hair loss |
| El Taieb (2017) [42] | 90 | AA | 43/57 | 10–40 |
MS (30) LR-PRP (30) |
Ca2+ activated | PBO (30) |
MS (30) LR-PRP (30) PBO (30) |
1 week | Hair growth; short vellus hair; hair dystrophy | 3 months | Patients treated with 5% MS and PRP both showed significantly greater hair growth compared to the PBO. Those treated with PRP exhibited an earlier response, including hair regrowth, reduction in short vellus hair, and improvement in dystrophic hair, unlike patients treated with minoxidil or the control group |
| Kachhawa (2017) [43] | 50 | AGA | 100/0 | 18–55 | LR-PRP (50) | Non-activated | PBO (50) |
LR-PRP (44) PBO (44) |
3 weeks; | Hair growth; hair loss (hair pull test); hair density; hair thickness; patient satisfaction; adverse effects | 6 months | PRP injections improved hair thickness and density, offering significant therapeutic benefits with minimal side effects and high overall patient satisfaction |
| Shah (2017) [44] | 50 | AGA | 100/0 | 18–50 | PRP + MN + MS (25) | Non-activated | MS (25) |
PRP + MN + MS (25) MS (25) |
1 month; 0.05 ml/cm2 | Patient’s assessment; investigator’s assessment | 6 months | There was a significant improvement in both the patient assessment and the investigator’s assessment in patients treated with PRP after 6 months |
| Tawfik (2017) [45] | 30 | AGA | 0/100 | 20–45 | LR-PRP (30) | Ca2+ activated | PBO (30) |
LR-PRP (30) PBO (30) |
2 weeks | Hair density; hair thickness; hair loss (hair pull test); patient’s satisfaction | 6 months | PRP significantly increased hair density and hair thickness |
| Toama (2017) [46] | 40 | AGA | 48/52 | 18–45 | LR-PRP (20) | Ca2+ activated | PBO (20) |
LR-PRP (20) PBO (20) |
2 weeks; < 0.1 ml/cm2 | Hair count; hair cross section; clinical evaluation; side effects | 6 months | PRP led to increased hair counts and improved emotional well-being in patients |
| Alves (2018) [47] | 25 | AGA | 46/54 | 18–65 | LP-PRP (25) | Ca2+ activated | PBO (25) |
LP-PRP (24) PBO (24) |
1 month; 0.15–0.20 ml/cm2 | Hair count; hair density; terminal hair density; anagen hair; telogen hair; anagen/telogen ratio | 6 months | PRP is an effective and safe complementary treatment for AGA; however, further long-term, placebo-controlled studies are needed to confirm its efficacy |
| Albalat (2019) [48] | 80 | AA | 85/15 | 17–52 | LR-PRP (40) | Ca2+ activated | ILC (40) |
LR-PRP (40) ILC (40) |
2 weeks; 0.1 ml/cm2 | Hair regrowth (SALT score and RGS score); hair dystrophy; side effects | 6 months | Both groups showed significant hair re-growth |
| Behrangi (2019) [49] | 120 | AGA | 100/0 | 20–40 |
FIN (30) PRP (30) |
Ca2+ activated | PBO (60) |
FIN (28) PRP (26) PBO (60) |
1 month | Hair growth; hair loss (hair pull test) | 6 months | PRP reduced hair loss and also promoted the hair re-growth process |
| Ranpariya (2019) [50] | 30 | AA | 73/27 | 20–40 | PRP (30) | Non-activated | ILC (30) |
PRP (30) ILC (30) |
3 weeks; 0.1 ml/cm2 | Hair regrowth; hair dystrophy; recurrences; adverse effects | 3 months | Intralesional triamcinolone acetonide is more effective than intralesional PRP in treating scalp alopecia areata, with no recurrences and minimal adverse effects |
| Rodrigues (2019) [51] | 30 | AGA | 100/0 | 18–50 | LR-PRP (15) | Non-activated | PBO (11) |
LR-PRP (15) PBO (11) |
2 weeks | Hair count; hair density; anagen hairs; telogen hairs | 2 months | The PRP group showed a significant increase in hair count, hair density, and the percentage of anagen hairs compared to the control group |
| Singh (2019) [52] | 80 | AGA | 100/0 | 18–60 |
MS (20) LR-PRP (20) LR-PRP + MS (20) |
Ca2+ activated | PBO (20) |
MS (17) LR-PRP (19) LR-PRP + MS (20) PBO (19) |
1 month; 0.05–0.1 ml/cm2 | Hair density, patient’s satisfaction; adverse effects | 5 months | PRP combined with topical minoxidil is more effective than either PRP or topical minoxidil alone for AGA |
| Aggarwal (2020) [53] | 44 | AGA | 100/0 | 22–44 | MN + PRP (22) | Non-activated | MN + PBO (22) |
MN + PRP (15) MN + PBO (15) |
1 month; 0.1 ml/cm2 | Hair thickness; hair density; patient’s satisfaction | 6 months | Both microneedling and PRP are effective in treating androgenetic alopecia, enhancing hair parameters and patient satisfaction, but PRP did not show any added benefit over microneedling |
| Balakrishnan (2020) [54] | 40 | AA | 73/27 | – | LR-PRP (20) | Non-activated | ILC (20) |
LR-PRP (16) ILC (16) |
4 weeks; 0.1 ml/cm2 | Hair regrowth (SALT score and RGS score) | 12 weeks | PRP is a safe, effective, steroid-sparing treatment and a viable alternative for alopecia areata (AA) |
| Bruce (2020) [55] | 20 | AGA | 0/100 | 20–79 | LR-PRP (20) | Non-activated | MS (20) |
LR-PRP (19) MS (18) |
4 weeks; 0.05–0.1 ml/cm2 | Hair count; vellus hair density; terminal hair density; cumulative thickness; patient’s satisfaction; adverse effects | 32 weeks | PRP is an effective treatment for hair regrowth in female AGA, though it may not be as effective as minoxidil. However, the improvement in quality of life reported after PRP treatment, which was not observed with minoxidil, suggests a potentially higher overall satisfaction with PRP." |
| Dicle (2020) [56] | 30 | AGA | 100/0 | 19–48 | LP-PRP (25) | Ca2+ activated | PBO (25) |
LP-PRP (25) PBO (25) |
1 month | Clinical assessment; hair count; side effects | 9 months | PRP significantly increased hair density and the proportion of patients with low grade alopecia |
| Dubin (2020) [57] | 30 | AGA | 0/100 | 27–85 | PRP (15) | Non-activated | PBO (15) |
LP-PRP (14) PBO (14) |
1 month; 0.05–0.1 ml/cm2 | Hair density; hair dystrophy; side effects | 24 weeks | PRP induced a statistically significant increase in mean total hair density in patients with female androgenetic alopecia (AGA) |
| Gressemberger (2020) [58] | 30 | AGA | 100/0 | 18–52 | PRP (20) | Non-activated | PBO (10) |
PRP (19) PBO (9) |
4–6 weeks; 0.1 ml/cm2 | Hair density; hair thickness; clinical improvement; patient’s satisfaction | 6 months | Platelet-rich plasma monotherapy does not enhance hair growth in men with AGA |
| Hegde (2020) [59] | 50 | AA | – | 18–60 |
PRP (25) ILC (25) |
Non-activated | PBO (25) |
PRP (25) ILC(25) PBO (25) |
4 weeks; 0.1 ml/cm2 | Hair regrowth (SALT score); hair dystrophy | 5 months | Hair regrowth and dermoscopic parameters were improved in patients treated with PRP, but maximum absolute regrowth was shown by the steroid group |
| Kapoor (2020) [60] | 40 | AA | 45/55 | 18–50 | PRP (20) | Non-activated | ILC (20) |
PRP (20) ILC (20) |
3 weeks | Hair regrowth (SALT score) | 6 months | Both intralesional triamcinolone and PRP were effective in treating alopecia areata, but PRP resulted in less improvement |
| Pakhomova (2020) [61] | 69 | AGA | 100/0 | 18–53 | PRP (25) | Ca2+ activated | MS (22) |
PRP (25) PRP + MS (22) MS (22) |
1 month | Hair density; hair diameter; clinical improvement; vellus hair; telogen hair; cell proliferation (β-catenin, CD34, Ki67, and to Dkk-1) | 4 months | A comparative analysis of treatment outcomes between minoxidil monotherapy and PRP monotherapy showed no significant difference in hair density alone. However, for other parameters, PRP demonstrated significantly greater efficacy (p ≤ 0.0243), supporting its potential as a promising treatment option for androgenetic alopecia (AGA) |
| Shapiro (2020) [62] | 35 | AGA | 51/49 | 18–58 | LP-PRP (35) | Non-activated | PBO (35) |
LP-PRP (35) PBO (35) |
1 month; 0.1 ml/cm2 | Hair density; hair diameter; patient’s satisfaction; side effects | 3 months | The difference in hair density change between the groups was not statistically significant |
| Siah (2020) [63] | 10 | AGA | 10/90 | 20–55 | LP-PRP | Non-activated | PBO |
LP-PRP (10) PBO (10) |
2 weeks; 0.1 ml/cm2 | Hair density; hair caliber; clinical improvement | 8 weeks | PRP treatment may be effective for AGA. Standardizing growth factors after PRP processing could help improve hair growth responses |
| Verma (2020) [64] | 40 | AGA | 100/0 | 20–49 | LR-PRP (20) | Ca2+ activated | MS (20) |
LR-PRP (16) MS (14) |
1 month; 0.1–0.2 ml/cm2 | Hair loss (hair pull test); hair growth questionnaire; patient’s satisfaction | 6 months | PRP therapy can be an effective adjunct to topical minoxidil in treating AGA |
| Fawzy (2021) [65] | 31 | AA | 74/26 | 21–45 | PRP | Non-activated | ILC |
PRP (14) ILC (17) |
1 month; 0.1 ml/cm2 | Hair regrowth (SALT score); clinical evaluation | 3 months | PRP was effective in treating patchy AA |
| Gupta (2021) [66] | 27 | AA | 48/52 | 18–35 | PRP (27) | Ca2+ activated | PBO (27) |
PRP (27) PBO (27) |
1 month | Hair regrowth (SALT score); hair dystrophy | 3 months | PRP was found to have limited effectiveness in AA |
| Qu (2021) [67] | 52 | AGA | 62/38 | – | LR-PRP (52) | Non-activated | PBO (52) |
PRP (52) PBO (52) |
1 month; 0.05–0.1 ml/cm2 | Hair count; hair density; hair diameter; anagen hair ratio; patient’s satisfaction; adverse effects | 6 months | PRP injections resulted in a significant increase in hair density at an early stage, followed by notable improvements in hair count, diameter, and the anagen hair ratio at 6 months, compared to the control side. Furthermore, all patients expressed satisfaction and reported no severe side effects |
| Ray (2021) [68] | 100 | AGA | 100/0 | 20–50 | LR-PRP + MS (50) | Ca2+ activated | MS (50) |
LR-PRP + MS (45) MS (45) |
4 weeks; 0.1 ml/ cm2 | Hair diameter; clinical improvement | The combination therapy was more effective than monotherapy in promoting hair growth in men with AGA | |
| Zhou (2021) [69] | 10 | AGA | 100/0 | 18–65 | LR-PRP (10) | Ca2+ activated | PBO (10) |
PRP (10) PBO (10) |
30 days; 0.1 ml/cm2 | Clinical improvement; patient’s satisfaction | 9 months | PRP can stimulate hair growth and is both safe and effective for treating AGA |
| Pachar (2022) [70] | 50 | AGA | 100/0 | 18–54 | MS + LR-PRP (50) | Non-activated | MS (50) |
MS + LR-PRP (44) MS (44) |
1 month | Hair loss (hair pull test); hair density; hair thickness; patient’s satisfaction | 6 months | Topical 5% minoxidil combined with intradermal PRP demonstrates greater efficacy than topical 5% minoxidil alone in treating AGA |
| Agarwal (2023) [71] | 26 | AGA | 0/100 | 18–53 | LP-PRP | Non-activated | MS (14) |
PRP + MS (12) MS (14) |
1 month; 0.1 ml/cm2 | Hair density; hair loss (hair pull test); patient’s satisfaction; side effects | 24 weeks | Combination therapy of minoxidil and PRP is effective for FPHL but does not surpass the efficacy of topical 2% MS |
| Asim (2023) [72] | 72 | AGA | 83/17 | 20–40 | PRP (36) | Non-activated | MS (36) |
PRP (36) MS (36) |
1 month | Hair loss (hair pull test) | 12 weeks | PRP therapy shows greater efficacy than MS in treating AGA, with improved patient compliance and overall satisfaction |
| Balasundaram (2023) [73] | 64 | AGA | 100/0 | 20–50 | LR-PRP (32) | Non-activated | MS (32) |
LR-PRP (25) MS (26) |
1 month; 0.1–0.2 ml/cm2 | Hair count; hair density; terminal hair count; hair density; clinical improvement; patient’s satisfaction; adverse effects | 24 weeks | PRP is effective in treating moderate androgenetic alopecia in men, although it may not be more effective than minoxidil. However, side effects are more common with PRP |
| Chuah et al. (2023) [74] | 55 | AGA | 62/38 | 23–70 | LP-PRP (55) | Activated | PBO (55) |
LP-PRP (50) PBO (50) |
3 weeks | Hair density; hair diameter; clinical improvement; patient satisfaction | 6 months | Platelet-rich plasma treatment demonstrated an early effect on hair density, with increases observed in male participants as soon as 3 months after administration |
| El-Dawla (2023) [75] | 30 | CTE | 0/100 | 18–49 | PRP (20) | Non-activated | PBO (10) |
PRP (10 + 10) PBO (10) |
4 weeks | Hair loss (hair pull test); frontal hair density; frontal hair thickness; temporal hair density; temporal hair thickness; clinical assessment; patient’s satisfaction | 3 months | Platelet-rich plasma may be a promising treatment for patients with chronic telogen effluvium, offering an excellent safety profile |
| Janaani (2025) [76] | 75 | AGA | 100/0 | 20–45 | MS + PRP (20) | Non-activated | MS (20 + 20) | MS (20 + 20) PRP + MS (20) | 4 weeks | Clinical improvement; terminal hair density; vellus hair density; adverse effects | 32 weeks | Combining PRP with topical minoxidil leads to greater increases in terminal hair density, whereas orally administered minoxidil is more effective in reducing vellus hair density |
aAlopecia: AA alopecia areata, AGA androgenetic alopecia, CTE chronic telogen effluvium
bIntervention group: PRP platelet-rich plasma, LR-PRP leukocyte-rich PRP, LP-PRP leukocyte-poor PRP, MN microneedling, FIN finasteride, PDRN polydeoxyribonucleotide
cControl group: PBO placebo, ILC intralesional corticosteroids, MS minoxidil, UNT untreated
Risk of Bias Assessment
Two reviewers (RT and MH) independently evaluated the risk of bias for each included study using the Revised Cochrane Risk of Bias Tool (RoB 2) for randomized trials [18]. Disagreements were resolved through discussion to reach a consensus.
Quality Assessment
Contour-enhanced funnel plots were generated to evaluate potential publication bias [19, 20]. Egger’s test for the intercept was conducted to quantify funnel plot asymmetry [21], and if significant, Duval and Tweedie’s trim and fill method was applied [22].
Statistical Analyses
Trial results for each quantitative outcome were combined using aggregate data. Continuous outcomes were expressed as change from baseline to obtain adjusted estimates of the treatment effect with the aim of mitigating potential randomization bias. Mean change from baseline was extracted from the selected studies when explicitly stated or estimated by subtracting the final mean from the baseline. When standard deviation (SD) from baseline or final measurements were not available, they were estimated from the reported median, range, interquartile range (IQR), and sample size using the method proposed by Wan et al. [23]. SD for Changes from baseline and final population parameters, 95% confidence intervals (95% CI), p values, or t values were computed according to the methods described by Higgins and Green [24]. When baseline and final measurements or changes from baseline were reported graphically via box plots, bar plots, or line plots, mean and SD for were extracted using WebPlotDigitizer [25]. Pooled estimates were reported as odds ratios (OR) for count data, along with the corresponding 95% CI. For continuous outcomes, effect sizes were summarized as mean difference (MD), with between-study variance estimated by the Sidik–Jonkman method and the Hartung–Knapp approach for random-effects meta-analyses [26, 27]. Statistical heterogeneity was assessed using the I2 statistic [28], and Cochran’s Q test for residual heterogeneity was also calculated [29]. Random-effects models were applied to test for overall effects and heterogeneity statistics across all outcomes at the last follow-up. When supported by available data, subgroup analyses were conducted to identify sources of heterogeneity based on control treatment. PRP activation status and alopecia subtype. Incomplete reporting and variability in study design limited the ability to assess the effect of PRP leukocyte content on efficacy and safety measures. Mixed model meta-regression analyses were conducted to assess the impact of continuous covariates (follow-up time points and PRP administration frequency) on the effect estimates of primary outcomes. Statistical analyses were conducted using the metafor [30], meta [31], and robvis [32] packages within the R computing environment (v. 4.3.2) [33].
Ethics/Ethical Approval
This article is based on previously conducted studies and does not contain any new studies with human participants or animals performed by any of the authors.
Results
Literature Search Results and Study Selection
Our literature search produced 7884 potentially relevant citations. After duplicates were removed and articles were screened for relevance, 105 full-text articles were evaluated. Ultimately, 43 studies met the inclusion criteria [34–76] and 41 of them were included in the quantitative synthesis [34–39, 41, 43–76] (Fig. 1). The key characteristics of these studies are summarized in Table 1. The studies collectively involved 1877 participants, with an age range of 10–79 years, with male participants comprising about 73% of the population and female participants about 27%. A total of seven studies focused on female alopecia (202 participants), whereas 18 studies included male participants exclusively (884 participants). However, Puig et al. [41], Balakrishnan et al. [54], and Qu et al. [67] did not report the age range of their study populations, which comprised a total of 61 male and 57 female participants with diagnosis of AA and AGA, and 32 male and 20 female participants with AGA, respectively. On the other hand, Hedge et al. [59] did not provide information on the age range of their study population (50 participants). Regarding the target population, most studies focused on adults (18–79 years) and two also investigated school-aged children and adolescents [42, 48]. The majority of studies focused on patients with AGA [35–41, 43–47, 49, 51–53, 55–58, 61–64, 67–74], whereas a total of nine studies included individuals with a diagnosis of AA [34, 42, 48, 50, 54, 59, 60, 65, 66], and one study enrolled patients with chronic telogen effluvium (CTE) [75].
Fig. 1.
PRISMA flow diagram illustrating the study selection process
The studies were also categorized on the basis of PRP administration frequency: 30 studies administered monthly doses [34–36, 38–40, 44, 47, 49, 52–57, 59, 61, 62, 64–73, 75, 76], two used weekly dosing [37, 42], five employed biweekly regimens [45, 46, 48, 51, 63], four followed a triweekly schedule [43, 50, 60, 74], one provided supplementation every 4 to 6 weeks [58], and another study used a single-dose approach [41]. Regarding the characteristics of the intervention group, a total of five studies evaluated a combined therapy of PRP and minoxidil (MS) [44, 52, 68, 70, 76] and two combined PRP with microneedling [39, 53], whereas another study investigated the effect of PRP and polydeoxyribonucleotide (PDRN) [37]. All the remaining studies included a intervention arm to evaluate PRP as a monotherapy [34–36, 38, 40–43, 45–52, 54–67, 69, 71–75]. In terms of administration route, all 43 studies used intradermal injections. Several studies did not provide dosages used, but the most common amount of PRP injected ranged from 0.05 to 0.2 ml/cm2. Considering the control groups, 26 studies used a placebo (PBO) [34–36, 38, 40–43, 45–47, 49, 51–53, 56–59, 62, 63, 66–69, 74, 75], while 17 provided active control treatment [37, 39, 44, 48, 50, 54, 55, 60, 61, 64, 65, 68, 70–73, 76], including five studies comparing PRP with intralesional corticosteroids (ILC) [48, 50, 54, 60, 65], 11 studies comparing PRP with minoxidil (MS) [39, 44, 55, 61, 64, 68, 70–73, 76], and one study comparing PRP with PDRN [37]. Outcome data were available for 1838 participants, representing 98% of the total study population.
Risk of Bias Assessment
Figure 2 summarizes the risk of bias assessments for the included studies. A total of 20 studies demonstrated low risk of bias related to randomization considering that the randomization method was explicitly provided [34, 36, 39, 41, 43, 45, 53, 55, 57–59, 61, 62, 66–68, 71, 73, 75, 76]. Moreover, other 19 studies stated that a randomization process was conducted, but they did not detail the specific randomization technique utilized, raising some concerns [35, 37, 38, 40, 42, 44, 46–52, 56, 60, 63, 64, 72, 74]. Finally, a total of four studies were classified as high risk of bias arising from the randomization process since they did not provide details on allocation or randomization technique was not specified and groups were imbalanced [54, 65, 69, 70]. Regarding bias due to deviations from intended interventions, all studies were rated as low risk. Low risk of bias due to missing outcome was identified in 26 studies [34–36, 38–40, 44–48, 50, 59–63, 65–69, 71, 72, 74–76], whereas 14 studies exhibited some concerns [37, 41–43, 49, 51, 52, 55–58, 70, 73] and a total of three [53, 54, 64] were judged to have a high risk of bias due to substantial missing outcome data (> 20%). On the other hand, most studies (26) were not blinded for patients and/or investigators and some of the outcomes were subjectively assessed, so they were rated as having some concerns in terms of bias concerning the measurement of the outcome [34, 39, 41, 43–46, 48–50, 53–60, 64–67, 69–71, 73]. The remaining 17 studies were considered as having low risk of bias since they were double blinded or the outcomes measured were objective [35–38, 40, 42, 47, 51, 52, 61–63, 68, 72, 74–76]. Considering selective reporting bias, most studies (35) were classified as low risk [34–36, 38–42, 44–48, 50–55, 57, 58, 60–69, 71, 72, 74, 75] and a total of eight were rated as raising some concerns since the approach to reporting the results of the analysis is unclear [37, 43, 49, 56, 59, 70, 73, 76].
Fig. 2.
Individual (a) and summarized (b) results of risk of bias assessment via Rob2 tool: This figure presents the review authors’ judgements for each risk-of-bias criterion, as assessed using the RoB 2 tool, for all included studies
Primary Outcomes
Because of inconsistent or absent reporting on PRP composition and leukocyte content, only the presence or absence of an activation step could be determined with confidence. For this reason, activation status was the only PRP manufacturing-related factor incorporated into subgroup analyses. Egger’s test did not yield statistically significant results for hair density or hair thickness, indicating the absence of significant publication bias (p > 0.05). The diagnostic plots and regression tests for asymmetry and meta-regressions are presented in the Supplementary Material. Graphical representations of meta-regressions are also provided as Supplementary Material. After examining aggregate data from 1198 participants from 24 studies, a significant overall increase in hair density was observed in patients with alopecia receiving PRP therapy (MD 19.6 [95% CI 6.4–32.8]; p = 0.0052; I2 = 93.5%) (Fig. 3a). Significant changes in subgroup effect estimates were identified across different control treatments (p < 0.0001). When compared with PBO, a meta-analysis involving 18 prospective controlled studies involving 883 participants revealed that PRP significantly improved hair density in patients with alopecia (MD 28.4 [95% CI 12.8–44.0]; p = 0.0013; I2 = 94.4%). In contrast, the effect sizes of PRP (either alone or in combination with active substances) and active controls (MS or PDRN) were equivalent: PRP vs MS (MD − 22.9 [95% CI − 50.8 to 5.0]; p = 0.071; I2 = 56.1%; pooled estimates from three studies involving 124 participants and PRP + MS vs MS (MD 10.9 [95% CI − 7.5 to 29.3]; p = 0.13; I2 = 2.9%; pooled estimates from three studies involving 151 participants). Regarding PRP with different activation states, no significant differences were observed in the hair density response to different PRP types (p = 0.71), indicating no strong evidence of effect modification (Fig. 3b). However, only activated PRP produced a significant effect on promoting hair density (MD 23.6 [95% CI 8.7–38.4]; p = 0.0050; I2 = 96.1%; estimates from 11 studies involving 554 participants) as revealed by subgroup analysis. This effect was not observed for non-activated PRP (MD 18.3 [95% CI − 6.5 to 43.0]; p = 0.13; I2 = 86.1%; estimates from 14 studies involving 644 participants). Stratified analysis by alopecia subtype could not be conducted, as the entire study population consisted of individuals with AGA. Meta-regression analyses revealed that the covariates follow-up time point (p = 0.78) and PRP administration frequency (p = 0.42) were not significantly associated with the effect size.
Fig. 3.
Forest plot of the meta-analysis on the effect of PRP alone or combined with other active substances vs control on hair density (change from baseline in hair count per square centimeter) across a different types of control treatment [placebo (PBO), polydeoxyribonucleotide (PDRN), or minoxidil (MS)] and b different states of PRP activation [activated PRP (aPRP) and non-activated PRP (uPRP)]. Squares represent individual study mean difference estimates (MD), with 95% confidence intervals [95% CI]. Square size reflects study weight extracted from random effects meta-analysis (W[%]). The vertical line indicates no effect, and the diamond shows individual subgroup and overall estimates
As depicted in Fig. 4, no significant overall effect was observed after comparing PRP with control treatment (MD 8.2 [95% CI − 4.3 to 20.7]; p = 0.18; I2 = 92.3%) in terms of hair thickness after pooling the effect size estimates of 13 studies involving 725 patients. Most studies reporting this outcome compared PRP with PBO (MD 10.3 [95% CI − 6.8 to 27.3]; p = 0.21; I2 = 93.9%; pooled estimates 10 studies involving 548 participants), while only one study reporting data from 40 patients compared the effect of PRP and PDRN with PDRN alone (MD − 1.1 [95% CI − 8.6 to 3.7]; p = 0.74; I2 = 0.0%) (Fig. 4a). Subgroup analyses confirmed no significant differences between PRP and control effect sizes, regardless of the type of control treatment (p = 0.38) or PRP activation status (p = 0.25). The following results were produced by different levels of the latter covariate: activated PRP (MD 19.2 [95% CI − 22.1 to 60.4]; p = 0.27; I2 = 96.0%; pooled estimates from five studies involving 548 participants) and non-activated PRP (MD 2.1 [95% CI − 1.8 to 6.0]; p = 0.24; I2 = 77.9%; pooled estimates from eight studies involving 398 participants) (Fig. 4b). Regarding the clinical form of alopecia, hair thickness measurements were exclusively documented in trials enrolling subjects with clinically confirmed AGA. Meta-regression analyses also indicated that the association between follow-up time point (p = 0.055) and PRP administration frequency (p = 0.32) and effect size estimates was not significant.
Fig. 4.
Forest plot of the meta-analysis on the effect of PRP alone or combined with other active substances vs control on hair thickness (change from baseline in micrometers) across a different types of control treatment [placebo (PBO) and the combined therapy vs polydeoxyribonucleotide (PRP + PDRN vs PDRN)] and b different types of PRP [activated PRP (aPRP) and non-activated PRP (uPRP)]. Squares represent individual study mean difference estimates (MD), with 95% confidence intervals [95% CI]. Square size reflects study weight extracted from random effects meta-analysis (W[%]). The vertical line indicates no effect, and the diamond shows individual subgroup and overall estimates
Secondary Outcomes
Egger’s test did not reveal statistically significant results for adverse effects, clinical improvement, hair loss, terminal hair density, vellus hair density, anagen hair, or telogen hair, indicating no strong evidence of publication bias (p > 0.05). In contrast, the outcomes SALT score, patient satisfaction, and recurrence yielded statistically significant results (p ≤ 0.05), suggesting potential evidence of publication bias. The diagnostic plots and regression tests for asymmetry and meta-regressions are presented in the Supplementary Material. Graphical depictions of the meta-analyses related to secondary outcomes are also included in this section. For the variable patient satisfaction, the trim and fill method was applied to address potential publication bias. This approach was used to adjust for any asymmetry in the funnel plot, providing a more accurate estimate by imputing missing studies that may not have been published as a result of non-significant findings. The trim and fill method was applied; however, with only nine studies included in the meta-analysis, which is below the recommended threshold (n = 10), the results must be interpreted with caution.
Meta-analyses of aggregate data with subgroups including studies that reported secondary discrete variables (count data) are summarized in Table 2. Additionally, graphical representations of meta-analysis and meta-regressions are provided as Supplementary Material. Overall, the proportion of patients who experienced at least one side effect was similar for PRP and control arms (OR 1.7 [95% CI 0.77–3.7]; p = 0.19; I2 = 61.5%; pooled estimates from 11 studies involving 587 participants). Adverse events, most commonly limited to transient pain during injection and shortly thereafter, injection site erythema, swelling, bruising, were generally mild and well tolerated by most patients, predominantly consisting of transient pain during injection and shortly thereafter, injection site erythema, swelling, or bruising. After the control treatments were evaluated individually, no significant differences were detected between PRP and PBO (OR 0.74 [95% CI 0.24–2.3]; p = 0.60; I2 = 0.0%; pooled estimates from three studies involving 110 participants), ILC (OR 3.0 [95% CI 0.64–14.0]; p = 0.16; I2 = 72.5%; pooled estimates from three studies involving 190 participants), MS (OR 2.1 [95% CI 0.73–5.9]; p = 0.17; I2 = 0.0%; pooled estimates from two studies involving 88 participants), or between PRP + MS and MS (OR 1.0 [95% CI 0.10–11.0]; p = 0.19; I2 = 80.6%; pooled estimates from three studies involving 159 participants). Nevertheless, subgroup comparisons revealed that the observed variation in treatment effects associated with control treatment was not significant (p = 0.50). Regarding the impact of PRP formulation on the incidence of side effects, subgroup analysis revealed that the effect size estimates significantly differ between PRP formulation types (p = 0.015). In this sense, the effect size estimates did not differ from control for activated PRP (OR 0.72 [95% CI 0.35–1.5]; p = 0.35; I2 = 0.0%; pooled estimates from five studies involving 316 participants). However, the effect size of PRP was significantly different from control treatment when non-activated PRP (OR 3.7 [95% CI 1.4–10.2]; p = 0.011; I2 = 53.3%) was administered as based on six studies involving 349 participants. Regarding alopecia subtype, the effect of subgroup stratification on the incidence of adverse events was not statistically significant (p = 0.50).
Table 2.
Summary of overall and subgroup meta-analytic random-effects models of discrete secondary outcomes (count data)
| N studies | Odds ratio | CI (95%) | p effect | I2 (%) | p heterogeneity | |
|---|---|---|---|---|---|---|
| Side effects | ||||||
| Overall | 12 | 1.7 | 0.77–3.7 | 0.19 | 61.5 | 0.0058 |
| Control treatmenta | ||||||
| PBO | 3 | 0.74 | 0.24–2.27 | 0.60 | 0.0 | 0.86 |
| PRP + PDRN vs PDRN | 1 | 6.0 | 1.1–33.3 | 0.04 | 0.0 | 1.0 |
| ILC | 3 | 3.0 | 0.64–14.0 | 0.16 | 72.5 | 0.01 |
| MS | 2 | 2.1 | 0.73–5.9 | 0.17 | 0.0 | 0.36 |
| PRP + MS vs MS | 3 | 1.0 | 0.10–11.0 | 0.97 | 80.6 | 0.022 |
| PRP typeb | ||||||
| aPRP | 6 | 0.72 | 0.35–1.5 | 0.39 | 19.5 | 0.35 |
| uPRP | 6 | 3.7 | 1.4–10.2 | 0.011 | 53.3 | 0.058 |
| Alopecia subtypec | ||||||
| AA | 4 | 2.67 | 0.68–10.5 | 0.16 | 61.4 | 0.034 |
| AGA | 8 | 1.34 | 0.51–3.5 | 0.55 | 58.7 | 0.025 |
| Hair loss | ||||||
| Overall | 6 | 0.14 | 0.02–0.94 | 0.043 | 83.5 | 0.0010 |
| Control treatment | ||||||
| PBO | 2 | 0.0 | 0.00–0.04 | < 0.0001 | 0.0 | 0.81 |
| MS | 2 | 0.22 | 0.08–0.63 | 0.0045 | 0.0 | 0.86 |
| PRP + MS vs MS | 2 | 1.0 | 0.30–3.5 | 0.96 | 0.0 | 0.41 |
| PRP type | ||||||
| aPRP | 3 | 0.11 | 0.01–2.2 | 0.15 | 87.5 | 0.0050 |
| uPRP | 3 | 0.16 | 0.01–4.1 | 0.27 | 84.4 | 0.0079 |
| Alopecia subtypec | ||||||
| CTE | 1 | 0.010 | 0.00–0.10 | 0.00047 | 0.0 | 1.0 |
| AGA | 5 | 0.24 | 0.040–1.4 | 0.12 | 79.7 | 0.0084 |
| Clinical improvement | ||||||
| Overall | 14 | 2.5 | 0.92–6.9 | 0.073 | 78.5 | < 0.0001 |
| Control treatment | ||||||
| PBO | 5 | 8.2 | 2.4–27.5 | 0.00066 | 67.7 | 0.029 |
| ILC | 4 | 0.57 | 0.06–5.3 | 0.62 | 69.9 | 0.0090 |
| MS | 3 | 0.53 | 0.23–1.2 | 0.12 | 0.0 | 0.19 |
| PRP + MS vs MS | 2 | 4.7 | 1.0–21.2 | 0.047 | 0.0 | 0.36 |
| PRP type | ||||||
| aPRP | 5 | 5.8 | 0.24–139 | 0.28 | 88.2 | < 0.0001 |
| uPRP | 9 | 2.2 | 0.86–5.8 | 0.0073 | 64.1 | 0.0073 |
| Alopecia subtypec | ||||||
| AA | 4 | 0.57 | 0.060–5.3 | 0.62 | 69.9 | < 0.0001 |
| AGA | 10 | 3.9 | 1.37–11.2 | 0.011 | 76.9 | < 0.0001 |
| Patient satisfaction | ||||||
| Overall | 9 | 2.3 | 1.3–3.9 | 0.0026 | 0.0 | 0.13 |
| Control treatment | ||||||
| PBO | 3 | 19.1 | 0.46–782 | 0.12 | 80.5 | 0.015 |
| ILC | 1 | 1.2 | 0.39–3.6 | 0.77 | 0.0 | 1.0 |
| MS | 2 | 3.4 | 0.88–12.8 | 0.077 | 0.0 | 0.73 |
| PRP + MS vs MS | 3 | 2.0 | 0.89–4.4 | 0.095 | 0.0 | 0.95 |
| PRP type | ||||||
| aPRP | 3 | 18.4 | 0.44–773 | 0.13 | 80.7 | 0.015 |
| uPRP | 6 | 1.9 | 1.0–3.4 | 0.039 | 0.0 | 0.90 |
| Alopecia subtypec | ||||||
| AA | 1 | 1.2 | 0.38–3.6 | 0.77 | 0.0 | 1.0 |
| AGA | 8 | 2.8 | 1.5–5.1 | 0.011 | 0.0 | 0.15 |
| Recurrence | ||||||
| Overall | 3 | 0.43 | 0.05–3.4 | 0.42 | 70.8 | 0.065 |
| PRP type | ||||||
| aPRP | 2 | 0.17 | 0.06–0.52 | 0.033 | 0.0 | 1.0 |
| uPRP | 1 | 7.8 | 0.38–157 | 0.18 | 0.0 | 1.0 |
aControl treatment abbreviations: PBO placebo, PRP + PDRN vs PDRN platelet-rich plasma and polydeoxyribonucleotide, ILC intralesional corticosteroids, MS minoxidil, PRP + MS vs MS platelet-rich plasma and minoxidil, FIN finasteride
bPRP type abbreviations: aPRP activated PRP, uPRP non-activated PRP
cAlopecia subtype: AA alopecia areata, AGA androgenetic alopecia, CTE chronic telogen effluvium
Meta-analyses including six studies involving 306 participants concluded that the administration of PRP in patients suffering alopecia significantly reduced overall hair loss (OR 0.14 [95% CI − 0.055 to 6.0]; p = 0.043; I2 = 0.0%). The test for subgroup differences regarding control treatment was statistically significant, indicating that the treatment effect varied across control types (p < 0.0001). The observed decrease in the rate of hair loss was particularly important when PRP was compared with PBO (OR 0.0 [95% CI 0.0–0.040]; p < 0.0001; I2 = 0.0%; pooled estimates from two studies involving 90 participants), but also with MS treatment (OR 0.22 [95% CI 0.08–0.63]; p = 0.0045; I2 = 0.0%; pooled estimates from two studies involving 102 participants). However, data indicate that the combination of PRP and MS did not provide any significant advantage when compared with MS alone (OR 1.0 [95% CI 0.10–11.0]; p = 0.97; I2 = 80.6%; pooled estimates from two studies involving 114 participants). PRP activation status-based subgroup analyses showed that both the effect of subgroup (p = 87) and the effect size estimates for specific PRP activation states were non-significant, including activated PRP (OR 0.11 [95% CI 0.01–2.2]; p = 0.15; I2 = 87.5%; pooled estimates from three studies involving 178 participants) and non-activated PRP (OR 0.16 [95% CI 0.01–4.1]; p = 0.27; I2 = 84.4%; pooled estimates from three studies involving 128 participants). No significant differences in hair loss were observed across alopecia subtypes following subgroup stratification (p = 0.87). Nevertheless, the interpretation of these findings is constrained by the inclusion of five studies focusing on AGA (OR 0.24 [95% CI 0.040–1.4]; p = 0.043; I2 = 83.5%; estimate from five studies involving 276 participants) and only one study specifically addressing CTE.
On the other hand, PRP administration did not result in a statistically significant clinical improvement overall considering a total of 14 studies involving 717 participants (OR 2.5 [95% CI 0.92–6.9]; p = 0.073; I2 = 78.5%). Nevertheless, a detailed statistical assessment showed that the effect of PRP on clinical improvement was significantly dependent on control type (p = 0.042). In this sense, PRP was associated with a statistically significant enhancement in clinical outcomes when compared with PBO (OR 8.2 [95% CI 2.4–27.5]; p = 0.00066; I2 = 67.7%; pooled estimates from six studies involving 234 participants). A milder positive effect of PRP on clinical improvement was observed after comparing a combined therapy of PRP and MS with MS-based monotherapy according to pooled estimates computed from two studies involving 130 participants (OR 4.7 [95% CI 1.0–21.2]; p = 0.047; I2 = 0.0%). On the other hand, when compared to active control interventions, PRP showed a similar effect on clinical improvement, including PRP vs ILC (OR 0.57 [95% CI 0.06–5.3]; p = 0.62; I2 = 69.9%; pooled estimates from four studies involving 212 participants) or PRP vs MS (OR 0.53 [95% CI 0.23–1.2]; p = 0.12; I2 = 0.0%; pooled estimates from three studies involving 141 participants). With regard to the specific effect of each PRP activation status on clinical improvement, subgroup analysis did not support the presence of effect modification (p = 0.99). The effect estimates were non-significant for both activated (OR 2.4 [95% CI 0.20–28.9]; p = 0.48; I2 = 87.0%; pooled estimates from five studies involving 338 participants) and non-activated PRP (OR 2.2 [95% CI 0.86–5.8]; p = 0.10; I2 = 64.1%; estimate from nine studies involving 379 participants). Considering alopecia classification, the quantitative synthesis revealed that clinical improvement did not differ significantly between alopecia subtypes following subgroup analyses (p = 0.99): AA (OR 0.57 [95% CI 0.060–5.3]; p = 0.073; I2 = 0.0%; estimate from four studies involving 212 participants) and AGA (OR 3.9 [95% CI 1.4–11.2]; p = 0.011; I2 = 76.9%; estimate from 10 studies involving 530 individuals).
Overall patient satisfaction was significantly higher within the PRP arm than in the control group (OR 0.83 [95% CI 0.29–1.4]; p = 0.0026; I2 = 0.0%; pooled estimates from nine studies involving 375 participants). Egger’s test was significant (p = 0.015), suggesting possible publication bias or small-study effects. Visual inspection of the funnel plot supports this finding. Further analysis using the trim and fill method was conducted to explore the impact of potential bias. After the trim and fill procedure was applied to correct the effect size under funnel plot symmetry, the overall effect size of PRP administration on patient satisfaction was still significant (OR 0.63 [95% CI 0.12–1.1]; p = 0.016; I2 = 0.0%. Although the trim and fill method was applied, the number of studies included in the meta-analysis (n = 9) is below the recommended threshold, and therefore the results should be interpreted with caution. As revealed by subgroup analyses, no effect modification was observed resulting from differences in control treatment (p = 0.28) or PRP formulation type (p = 0.40). Regarding control treatment, the calculated effect sizes estimates were as follows: PBO (OR 19.1 [95% CI 0.46–782]; p = 0.12; I2 = 0.0%; pooled estimates from three studies involving 92 participants), MS (OR 3.4 [95% CI 0.88–12.8]; p = 0.077; I2 = 0.0%; pooled estimates from a two studies involving 80 participants), and PRP + MS vs MS (OR 2.0 [95% CI − 0.89 to 4.4]; p = 0.095; I2 = 0.0%; pooled estimates from three studies involving 153 participants). On the other hand, the effect of subgroup was also non-significant when considering specific PRP activation status (p = 0.11), including activated PRP (OR 18.4 [95% CI 0.44–773]; p = 0.13; I2 = 80.7%; pooled estimates from a two studies involving 107 participants) and non-activated PRP (OR 1.9 [95% CI 1.0–3.4]; p = 0.039; I2 = 0.0%; pooled estimates from six studies involving 268 participants). The role of alopecia subtype in modulating PRP effect size was assessed via subgroup analysis, which demonstrated no statistically significant variation in patient satisfaction between subgroups (p = 0.11). However, interpretation is limited by the fact that only a single study involving 50 patients specifically focused on AA, while the remaining eight studies involved a total 325 with a diagnosis of AGA (OR 2.8 [95% CI 1.5–5.1]; p = 0.0011; I2 = 0.0%).
The impact of PRP on overall recurrence as reported by a total of three studies including 170 patients was also not significant (OR 0.43 [95% CI 0.05–3.4]; p = 0.42; I2 = 70.8%), with no significant results after conducting the test for subgroup differences (p = 0.42). However, only activated PRP (OR 0.17 [95% CI 0.06 to − 0.52]; p = 0.019; I2 = 0.0%) tended to reduce significantly the incidence of recurrence as summarized from two studies involving 30 and 80 participants, respectively. This effect was not observed for non-activated PRP (OR 7.8 [95% CI 0.38–157]; p = 0.18; I2 = 0.0%). The homogeneity of the study populations with respect to alopecia subtype (only AA) limited the possibility of subtype-based stratification. Although funnel plot asymmetry was detected, the trim and fill method was not applied as a result of the small number of studies, which limits the reliability of this procedure. Thus, potential publication bias cannot be ruled out, but no correction was performed.
Focusing on the continuous secondary outcomes (Table 3), no significant differences were detected between PRP and control treatments in terms of SALT score overall (MD 2.4 [95% CI − 36.2 to 41.0]; p = 0.87; I2 = 92.3%; pooled estimates from five studies involving 235 participants), regardless of the control treatment identity: PBO (MD − 15.8 [95% CI − 250.9 to 220.4]; p = 0.55; I2 = 96.2%; pooled estimates from two studies involving 84 participants) and ILC (MD 18.7 [95% CI − 55.8 to 92.2]; p = 0.39; I2 = 76.2%; pooled estimates from three studies involving 151 participants). PRP effects did not vary significantly across control subgroups, as indicated by a non-significant test for interaction (p = 0.17). Considering PRP type, the effect of subgroup was significantly different as revealed by the test for subgroup differences (p < 0.0001). Non-activated PRP did result in a significantly lower reduction in SALT score in reference to baseline when compared with control treatment as concluded from two studies involving 71 participants (MD 43.3 [95% CI 6.2–80.4]; p = 0.042; I2 = 0.0%). Conversely, no statistically significant differences in the change in SALT score from baseline were observed for activated PRP compared to the control group (MD − 13.4 [95% CI − 62.4 to 35.6]; p = 0.36; I2 = 91.5%; estimates from three studies involving 164 participants). Similarly, the overall effect of PRP on terminal (MD 10.6 [95% CI − 10.2 to 31.4]; p = 0.23; I2 = 97.6%; estimates from four studies involving 181 participants) and vellus hair density (MD 11.4 [95% CI − 20.0 to 41.7]; p = 0.18; I2 = 0.0%; estimates from three studies involving 98 participants) was not significant. A significant effect of control treatment in was observed terminal hair density (p = 0.0084) but not in vellus hair density (p = 0.72). The observed effect on terminal (MD 18.0 [95% CI − 18.0 to 54.0]; p = 0.16; I2 = 98.7%; estimates from three studies involving 104 participants) and vellus hair density (MD 13.4 [95% CI − 100.0 to 126.7]; p = 0.38; I2 = 0.0; estimates from two studies involving 60 participants) was not significant for PBO. As all studies enrolled only patients with AA, stratified analysis by alopecia subtype was not applicable.
Table 3.
Summary of overall and subgroup meta-analytic random-effects models of continuous secondary outcomes
| N studies | Mean difference | CI (95%) | p effect | I2 (%) | p heterogeneity | |
|---|---|---|---|---|---|---|
| SALT score | ||||||
| Overall | 5 | 2.4 | − 36.2 to 41.0 | 0.87 | 92.3 | 0.0001 |
| Control treatment | ||||||
| PBO | 2 | − 15.8 | − 250.9 to 220.4 | 0.55 | 96.2 | 0.66 |
| ILC | 3 | 18.7 | − 54.8 to 92.2 | 0.39 | 76.2 | < 0.0001 |
| PRP type | ||||||
| aPRP | 3 | − 13.4 | − 62.4 to 35.6 | 0.36 | 91.5 | < 0.0001 |
| uPRP | 2 | 43.3 | 6.2–80.4 | 0.043 | 0.0 | 0.84 |
| Terminal hair density | ||||||
| Overall | 5 | 10.6 | − 10.2 to 31.4 | 0.23 | 97.6 | < 0.0001 |
| Control treatment | ||||||
| PBO | 3 | 18.0 | − 18.0 to 54.0 | 0.16 | 98.7 | < 0.0001 |
| MS | 1 | − 13.5 | − 28.0 to 0.95 | 0.034 | 0.0 | 1.0 |
| PRP + MS vs MS | 1 | 9.0 | 0.82–17.2 | 0.031 | 0.0 | < 0.0001 |
| PRP type | ||||||
| aPRP | 3 | 18.0 | − 18.0 to 54.0 | 0.16 | 98.7 | < 0.0001 |
| uPRP | 2 | − 1.36 | − 144 to 141 | 0.92 | 85.8 | 0.0079 |
| Vellus hair density | ||||||
| Overall | 3 | 11.4 | − 12.8 to 35.5 | 0.72 | 0.0 | 0.62 |
| Control treatment | ||||||
| PBO | 2 | 13.4 | − 100.0 to 126.7 | 0.38 | 0.0 | 0.36 |
| MS | 1 | 7.1 | − 12.8 to 35.5 | 0.59 | 0.0 | 1.0 |
| PRP type | ||||||
| aPRP | 2 | 13.4 | − 100.0 to 126.7 | 0.38 | 0.0 | 0.36 |
| uPRP | 1 | 7.1 | − 12.8 to 35.5 | 0.59 | 0.0 | 1.0 |
| Anagen hair | ||||||
| Overall | 4 | 3.8 | − 2.8 to 10.5 | 0.16 | 83.4 | 0.00040 |
| Control treatment | ||||||
| PBO | 3 | 6.4 | 3.8–9.0 | 0.0089 | 0.0 | 0.85 |
| MS | 1 | − 1.1 | − 3.0 to 0.79 | 0.23 | 0.0 | 1.0 |
| PRP type | ||||||
| aPRP | 1 | 7.0 | 2.94–11.1 | 0.0015 | 0.0 | 1.0 |
| uPRP | 3 | 2.7 | − 8.2 to 13.4 | 0.39 | 76.5 | 0.014 |
| Telogen hair | ||||||
| Overall | 3 | − 9.2 | − 17.5 to − 0.95 | 0.041 | 8.3 | 0.34 |
| Control treatment | ||||||
| PBO | 2 | − 9.6 | − 62.1 to 42.9 | 0.26 | 50.5 | 0.16 |
| MS | 1 | − 8.8 | − 11.3 to − 6.3 | < 0.00010 | 0.0 | 1.0 |
| PRP type | ||||||
| aPRP | 2 | − 9.9 | − 35.1 to 15.2 | 0.13 | 27.5 | 0.24 |
| uPRP | 1 | − 5.1 | − 10.3 to 0.11 | 0.055 | 0.0 | 1.0 |
aControl treatment abbreviations: PBO placebo, ILC intralesional corticosteroids
bPRP type abbreviations: aPRP activated PRP, uPRP non-activated PRP
The effect of PRP activation status on terminal hair density was not significant (p = 0.72). Subgroup analyses revealed that neither activated PRP (MD 18.0 [95% CI − 18.0 to 54.0]; p = 0.16; I2 = 98.7%; estimates from three studies involving 104 participants) nor non-activated PRP (MD − 1.4 [95% CI – 144 to 141]; p = 0.92; I2 = 85.8%; estimate from two studies involving 77 participants) resulted in a significantly different effect compared to the control group. Subgroup analyses also revealed that the effect of individual PRP activation states on vellus hair density was not significant for activated PRP (MD 13.4 [95% CI − 100.0 to 126.7]; p = 0.38; I2 = 98.7%; estimates from two studies involving 60 participants), indicating that the treatment effect was not consistent across all subgroups (p = 0.72). All included studies reporting terminal and/or vellus hair density focused solely on patients with AGA, precluding stratification by alopecia subtype.
With respect to hair growth phases, no significant overall effect of PRP treatment was identified via random effect meta-analyses for anagen hair (MD 3.8 [95% CI − 2.8 to 10.5]; p = 0.16; I2 = 83.4%; pooled estimates from four studies involving 168 participants), whereas a significant reduction in telogen hair was confirmed in response to PRP-based therapy (MD − 9.2 [95% CI − 17.5 to − 0.95]; p = 0.041; I2 = 8.3%; pooled estimates from three studies involving 95 participants). A significant association between effect size and PBO was observed for anagen hair (MD 6.4 [95% CI 3.8–9.0]; p = 0.0089; I2 = 0.0%; pooled estimates from three studies involving 175 participants). Similarly, the response of anagen hair to PRP and control was comparable across PRP activation states: non-activated PRP (MD 2.7 [95% CI − 8.2 to 13.4]; p = 0.39; I2 = 76.5%; pooled estimates from three studies involving 182 participants), with non-significant differences between subgroup estimates (p = 0.19). When compared with PBO, telogen hair did not show a significant reduction after PRP administration (MD − 9.6 [95% CI − 62.1 to 42.9]; p = 0.26; I2 = 50.5%; pooled estimates from two studies involving 70 participants). Nevertheless, the effect of control treatment-based subgroups (p = 0.84) and PRP formulation type (p = 0.33) were not significant for telogen hair. With reference to PRP activation status, activated PRP did not significantly reduce telogen hair when compared with control (MD − 9.9 [95% CI − 35.1 to 15.2]; p = 0.13; I2 = 27.5%) as concluded from two studies involving 44 participants.
Discussion
Currently, no systematic review with meta-analytic synthesis has addressed the effect of PRP-based interventions for alopecia considering the heterogeneity introduced by variations in control group design and PRP formulation type. The results of this systematic review and meta-analysis provide compelling evidence regarding the efficacy of PRP therapy in treating alopecia, particularly in improving hair density. Our analysis included 43 studies involving 1877 participants, representing a diverse population across age groups (10–79 years) and genders. This wide demographic distribution improves the overall relevance of the results. Despite heterogeneity across trials was significant, PRP therapy significantly increased hair density compared to placebo, with an overall MD of 19.6 [95% CI 6.4–32.8], confirming its effectiveness in promoting hair growth. This aligns with previous studies considering PRP as a promising treatment for alopecia [13, 77, 78]. Notably, when compared with active treatments, such as minoxidil (MS) or PDRN, PRP demonstrated a more modest effect, with no significant differences between treatment and control groups. These findings support that PRP therapy could be as effective as conventional therapy in promoting hair density, and indicates that combination therapies may not necessarily offer enhanced outcomes over PRP monotherapy.
Despite the fact that activated PRP formulations significantly improved hair density (MD 23.6 [95% CI 8.7–38.4]) whereas non-activated PRP formulations did not show the same positive results, the overall test for subgroup differences (i.e., the interaction test) was not statistically significant. The absence of a significant interaction implies that the observed variation may reflect random fluctuations or differences in statistical power and precision across subgroups. This is probably associated with the reduced statistical power inherent to smaller subgroup samples. Moreover, the observed heterogeneity in effect sizes may arise from differences in experimental design—such as PRP preparation protocol, administration dosage and frequency, specific composition of PRP, trial duration, and methods of assessing clinical outcomes—as well as from variations in population characteristics, including sex, ethnicity, socioeconomic status, dietary habits, health status, geographic location, disease subtype and grade, and other potential effect modifiers of PRP administration. Therefore, these results should be interpreted with caution and viewed as hypothesis-generating rather than confirmatory. Although the interaction test was not significant, the consistency of effects within activated PRP subgroups may point to a more uniform treatment response in these populations. This would be consistent with the hypothesis that platelet activation, which enhances the release of growth factors, may be essential for optimizing PRP’s therapeutic effect. As a consequence, the absence of strong subgroup effects does not imply a lack of efficacy, but rather highlights the need for larger, better-powered studies to establish differential responses and optimize treatment strategies.
According to Morkuzu et al. [79], activated PRP was significantly effective for improving both hair density (MD 46.5, 95% CI 29.63; I2 = 88%; p < 0.00001) and terminal hair density (MD 26.03, I2 = 25%, 95% CI 8.08–43.98, p = 0.004). The activation of PRP using agents like calcium, thrombin, collagen, or exogenous sources has been widely studied as a method to enhance its biological efficacy, primarily by accelerating the release of growth factors and cytokines [80]. Activation of PRP induces the release of platelet α--granules, which contain essential proteins for tissue repair and regeneration, thereby amplifying its biological effects compared to non-activated PRP [81]. Recent studies have demonstrated that PRP activation improves cellular proliferation and fibroblast migration, critical processes for dermal tissue regeneration in conditions such as androgenetic alopecia [82]. Additionally, activation enhances the concentration of growth factors like TGFβ, EGF, VEGF, and PDGF, which are essential for angiogenesis and wound healing [83, 84]. Nevertheless, the potential effect of non-activated PRP on alopecia-related outcomes was not assessed in the systematic review and meta-analysis mentioned above.
Conversely, Gentile et al. [85] suggested that growth factor concentrations within activated PRP did not display statistically significant differences in terms of growth factor profile or clinical effectiveness suggesting that PRP does not need to be activated to achieve therapeutic results. The results of this study are particularly relevant since they encompassed several standardized protocols for PRP preparation. These results were partially confirmed by Nouh et al. [86], who concluded that activating PRP may not significantly enhance its clinical improvement rate compared to non-activated PRP. In the same vein, different studies have shown that platelets in blood samples may undergo activation as a result of factors related to the preparation process, including manual handling, temperature variations, and the pressure applied during needle insertion. This evidence suggests that activating platelets with thrombin or calcium chloride prior to PRP injection procedure might not be a critical step [87]. Additionally, there is some evidence indicating that platelets injected into the human deep dermis and subdermal layers become activated when they come into contact with fibroblasts [88]. This finding highlights the complexity and variability in PRP research, where results can differ according to factors such as preparation methods, activation protocols, and specific clinical applications. The primary distinction of the present systematic review compared with those previously mentioned [78, 79, 85] is that no restrictions were applied regarding alopecia type, and potential effect-modifying covariates—such as the control intervention, PRP activation status, and alopecia type—were systematically examined. Furthermore, a meta-regression approach was performed to evaluate the influence of supplementation frequency and study duration on effect size.
On the other hand, the present meta-analysis revealed no significant differences between PRP and control groups in terms of hair thickness, suggesting that while PRP may help in hair density, its impact on the diameter of individual hair strands might be less pronounced. The heterogeneity is particularly high for hair thickness as a result of the huge effect size estimate reported by Tawfik et al. [45], who noted that hair thickness doubled in response to PRP. In this particular case, the observed differences in hair thickness between different ethnicities, population groups, scalp regions, age, and evaluation methods may significantly contribute to the variability observed among different studies [89–91]. These findings diverge from those of Evans et al. [78], who concluded that PRP induced a significant increase in hair thickness of 49%. However, when we examine the characteristics of this study in detail, we can observe that these conclusions derived from a highly heterogenous meta-analysis based on final absolute measurements involving only two studies (I2 = 97%), one of which reported hair thickness measurements at different time points, thus contributing to data bias since no statistical adjustment approaches were conducted for dealing with temporal dependence [92].
Considering that PRP therapy utilizes a patient’s own platelets, the likelihood of systemic adverse effects is minimal. Nevertheless, localized side effects such as pain and discomfort, minor bleeding, bruising, burning, erythema, or site-specific infections can still arise. In terms of safety, our meta-analysis found no significant differences in the incidence of side effects overall between PRP and control treatments, with a similar occurrence of adverse events across all treatment arms. These findings confirm that PRP is generally well tolerated and does not introduce significant safety concerns when compared with placebo or active treatments like minoxidil or intralesional corticosteroids. According to Lee et al. [37], when PRP was combined with PDRN, the incidence of side effects appeared to be reduced, suggesting that this combination could potentially be a safer option, but further research is needed to confirm these findings. An important observation emerging from these results is that patients treated with non-activated PRP tended to experience a significant increase in side effects as can be inferred from Agarwal et al. [71], Balasundaram et al. [73], Bruce et al. [55], Hedge et al. [59], and Lee et al. [37]. Despite evidence suggesting that activation status does not significantly impact the safety profile of PRP treatments (Nouh et al. [86]), the influence of activation on growth factor release and inflammatory response modulation should be further explored. However, most studies did not consider adverse events as primary or secondary outcomes, resulting in sparse and inconsistent safety reporting. This lack of standardized data collection contributed to the low confidence in the available evidence on adverse effects, largely due to heterogeneity in reporting and limited precision. In this sense, variability in how adverse events are defined, measured, and expressed across studies makes data synthesis and comparability difficult. Systematic and standardized event reporting—both in terms of overall incidence and event-specific data—would enable more detailed subgroup analyses, including stratification by severity categories or risk profiles. Consistently, subgroup analyses showed that only activated PRP was significantly associated with a reduction in recurrence rate (OR 0.17 [95% CI 0.06–0.52]), whereas studies administering non-activated PRP demonstrated a significantly higher decrease in SALT score compared to control group (MD 43.3 [95% CI 6.2–80.4]).
Furthermore, PRP therapy has been demonstrated to be significantly more effective in reducing hair loss than placebo or minoxidil. Similar conclusions were drawn by Gentile and Garcovich [93] after comparing the safety and effectiveness of PRP therapy with active controls including minoxidil, finasteride, and stem cell-based therapy. Accordingly, telogen hairs were reduced after PRP administration regardless of the control treatment considered whereas anagen hairs increased when comparing with placebo control, which aligns with observations reported by multiple authors [94]. Clinical improvement according to investigators’ assessment was also enhanced when compared with placebo (MD 8.2 [95% CI 2.4–27.5]) and also the combined therapy compared with minoxidil (MD 4.7 [95% CI 1.0–21.2]), whereas patient satisfaction was higher after PRP administration regardless of the control treatment or the specific PRP formulation type used (MD 2.3 [95% CI 1.3–3.9]). These findings indicate that PRP treatment is significantly more effective than placebo in improving clinical outcomes and yields clinical effects similar to those of active treatments, along with higher levels of patient-reported satisfaction. Further evidence for the effectiveness of PRP is provided by the significant reduction in telogen-phase hair (MD − 9.2 [95% CI − 17.5 to − 0.95]) and the increase in anagen-phase hair relative to placebo (MD 6.4 [95% CI 3.8–9.0]).
Although AGA, AA, and TE exhibit distinct etiologies—ranging from hormonal miniaturization to autoimmune and stress-induced dysregulation—the subgroup analysis revealed no significant modification of PRP efficacy or safety by alopecia subtype. Although constrained by heterogeneity in experimental designs and imbalanced alopecia subtype representation, this preliminary finding suggests that PRP’s therapeutic action may involve fundamental biological processes common to various alopecia forms. These include the stimulation of dermal papilla cells, promotion of angiogenesis via VEGF, modulation of inflammation through cytokine balance, and activation of follicular stem cells and the Wnt/β-catenin pathway, which are all relevant across different alopecia mechanisms [95–97]. Therefore, despite clinical and etiopathogenic differences, the shared regenerative pathways targeted by PRP could explain its consistent effects across subtypes. This hypothesis is supported by emerging evidence indicating that PRP exerts pleiotropic effects capable of benefiting diverse forms of hair loss regardless of their primary etiology [12]. In summary, current data demonstrate that PRP therapy reduces hair loss more effectively than placebo, with comparable clinical outcomes to active treatments such as minoxidil, finasteride, and intralesional corticosteroids. This is substantiated by consistent increases in hair density, improved clinical outcomes, and positive changes in hair growth stages. Moreover, PRP treatment is associated with greater patient satisfaction regardless of formulation or control interventions, underscoring its potential as a safe and effective therapeutic option for hair loss management. Nevertheless, subgroup analyses demonstrated that PRP activation status could significantly modulate the effectiveness and safety profile of PRP therapy.
Clinical Applicability
The results discussed above provide a basis for preliminary guidelines in reference to the use of PRP therapy for the treatment of alopecia. Reductions in hair loss and in the proportion of hairs in the telogen phase following PRP administration were higher than those observed after using conventional pharmacologic treatments, whereas other outcomes, including hair density, patient satisfaction, and adverse effects, were comparable between PRP and conventional pharmacologic treatments. Specifically, activated PRP has been demonstrated to provide superior results in terms of recurrence and side effect incidence, and is also the only formulation that has been associated with significant increases in hair density. Despite the fact that meta-regressions failed to detect a significant effect of supplementation frequency or study duration on primary outcomes, the majority of the available evidence is derived from studies in which the application frequency ranging from 2 to 4 weeks. These findings suggest that PRP injections could be considered a valuable therapeutic intervention in the treatment of alopecia, regardless of specific hair loss subtypes. However, these general guidelines should be interpreted with caution and revisited as more high-quality evidence emerges, particularly from studies investigating less common forms of alopecia that are underrepresented in this review. It is critical that future research provides comprehensive reporting of PRP composition and preparation methods, administration regimens, outcome quantification methods, and population demographics. Such methodological rigor and transparency will allow future meta-analyses and evidence syntheses to stratify results on the basis of important covariables and potential effect-modifiers, ultimately guiding the optimal clinical use of PRP therapies.
Systematic Review Limitations
Several limitations must be considered when interpreting these results. First, the included studies exhibited significant variability in terms of treatment protocols (e.g., PRP preparation protocol, frequency of administration, PRP composition, dosages), population characteristics (age, gender, ethnicity, alopecia subtype and severity), and efficacy outcomes assessment, which may contribute to the heterogeneity in effect sizes. Secondly, as a result of insufficient reporting in most studies, the impact of leukocyte inclusion on effect size could not be determined, despite its critical role in modulating inflammation, tissue repair, and regeneration. Additionally, the reporting in specific subgroups was often limited to a single study, which further undermines the reliability of the findings. This variability in study design, methods, and outcome reporting makes it difficult to draw definitive conclusions or generalize the results across different populations or treatment protocols. Moreover, while numerous studies assessed parameters using both qualitative and quantitative tools, inconsistencies in outcome measurement techniques across investigations created substantial challenges in drawing meaningful comparisons regarding treatment efficacy for alopecia. Despite the fact that subgroup analyses and meta-regression were computed to account for some of these differences, the high heterogeneity values in most outcomes suggest that further studies are needed to standardize experimental designs. Additionally, the lack of blinding in many studies introduces the potential for bias, especially in subjective qualitative outcome measures like clinical assessments, which may have influenced the results.
The interpretation of subgroup effects following stratification by alopecia subtype is inherently limited by the marked imbalance in the number of studies per condition, with androgenetic alopecia being disproportionately represented, while other subtypes—such as alopecia areata and telogen effluvium—remain significantly underrepresented. Additionally, substantial heterogeneity across study designs introduces methodological noise that further limits the statistical power and external validity of between-subgroup comparisons. Consequently, the absence of a significant interaction between alopecia type and treatment effect should be interpreted with caution, as it may reflect limitations in subgroup analysis due to design imbalance and insufficient stratified data, rather than a true biological equivalence of PRP efficacy and safety across etiologies. Future studies should focus on addressing the variability between PRP treatment protocols, including standardized methods for PRP preparation and platelet activation, optimal dosage, and administration frequency. Furthermore, research should investigate the long-term effects of PRP therapy and whether its benefits persist over time, as the duration of effect remains unclear. Additionally, randomized controlled trials with larger sample sizes and rigorous blinding are necessary to confirm the findings of this meta-analysis and further refine the clinical guidelines for PRP use in alopecia treatment.
Conclusions
The present systematic review and meta-analysis supports the efficacy of PRP as a promising therapeutic agent for the management of varying alopecia subtypes. Despite uncertainty regarding the effect of PRP on hair thickness, intradermal administration of activated PRP preparations contributes to improvements in hair density, reduction in hair loss, clinical outcomes, and patient satisfaction. Some of the observed effects are evident not only in placebo-controlled comparisons but also in comparisons with active controls. The overall safety profile of PRP is favorable, with no major differences in adverse events when compared with placebo or active treatments. Combining PRP with other active agents did not demonstrate significant additional benefits. The observed variability in effect size estimates suggests that differences in PRP composition and administration procedures could significantly impact its effectiveness. Studies have shown that PRP composition can vary according to the preparation methods, patient-specific factors such as age and baseline platelet count, and the specific techniques used. The general safety profile of PRP is favorable, with no significant differences in adverse events compared with placebo or active medications. The combination of PRP with other active treatments is not associated with additional significant benefits. Evidence of variability in effect size estimates indicates that heterogeneity in PRP composition, preparation methods, and administration regimens can influence efficacy. PRP composition can also vary according to preparation methods, patient-specific factors such as age, disease status, and baseline platelet count, and the specific administration techniques applied. These variations likely contribute to inconsistent clinical outcomes and underscore the need for standardized procedures to optimize PRP therapy. Overall, the strength and consistency of current evidence support PRP as a safe and effective therapy for treating hair loss, although further high-quality studies are necessary to assess the long-term sustainability of its effects.
Supplementary Information
Below is the link to the electronic supplementary material.
Acknowledgments
Medical Writing/Editorial Assistance
The authors confirm that the manuscript was refined using AI-assisted copy-editing tools to enhance readability, correct grammar/spelling, and improve stylistic flow. Such interventions were exclusively editorial and did not involve any generative content creation, data analysis, interpretation, or authorship. All final edits were reviewed, approved, and remain the original work of the authors, who take sole responsibility for the scientific content, methodology, and conclusions.
Author Contributions
Conceptualization: Eduardo Anitua and Mohammad Hamdan Alkhraisat, Literature search and data analysis: Mohammad Hamdan Alkhraisat and Roberto Tierno; Writing—original draft preparation: Mohammad Hamdan Alkhraisat and Roberto Tierno; Writing—review and editing: Eduardo Anitua and Mohammad Hamdan Alkhraisat, Supervision: Eduardo Anitua and Mohammad Hamdan Alkhraisat.
Funding
No funding or sponsorship was received for this study or publication of this article. The Rapid Service Fee was funded by the authors.
Data Availability
The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.
Declarations
Conflict of Interest
The authors declare the following competing financial interests: Eduardo Anitua is the Scientific Director of BTI Biotechnology Institute and Roberto Tierno and Mohammad Hamdan Alkhraisat are scientists at BTI Biotechnology Institute, a dental implant company that investigates in the fields of oral implantology and PRGF-Endoret® technology.
Ethics/Ethical Approval
This article is based on previously conducted studies and does not contain any new studies with human participants or animals performed by any of the authors.
Footnotes
Publisher’s Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
Data Availability Statement
The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.