Visible Light in the Treatment of Acne Vulgaris

Abstract

Acne vulgaris, a prevalent dermatological disorder, frequently affects individuals’ self-perception and general psychosocial functioning. The growing demand for home-based light therapy devices prompted a systematic review to assess the efficacy of visible light in acne treatment. Overall, 35 studies were included, representing 1185 cases of acne vulgaris (mean age: 23.7 years; sex: 63% female). A total of 69% of the included studies were level 2 evidence. Overall, 92% of patients achieved partial remission of their acne lesions using visible light therapy. Among the patients who experienced a partial remission of their acne, 46% experienced a reduction of 0% to 50% in their acne lesions, while 33% and 12% experienced reductions of 51% to 74% and 75% to 99%, respectively. Notably, blue light emerged as the predominant treatment modality in this context, used in around 64% of the cases. A total of 95% of the patients who were treated with blue light experienced a partial clearance of acne lesions; 44% experienced a reduction of 0% to 50% in their acne lesions, while 42% and 9% experienced reductions of 51% to 74% and 75% to 99%, respectively. Overall, the average total lesion count improved by 43% at week 4 compared to the baseline. The average number of treatment sessions was 22 (range 1-112 sessions). On average, treated patients responded within a period of 4 weeks. Commonly reported side effects included skin irritation and erythema. This review highlights the potential of visible light therapy in acne treatment. Head-to-head studies are needed to compare the efficacy of visible light compared to existing therapies for the treatment of acne.

Introduction

Acne vulgaris is a prevalent skin condition, commonly manifesting as comedones, inflammatory papules, and pustules. Predominantly observed in adolescents, it can also affect individuals across all age groups. ¹ The etiology of acne vulgaris encompasses hormonal, bacterial, and inflammatory components leading to excessive androgen-driven sebum production, follicular plugging, and the proliferation of Cutibacterium acnes, formerly Propionibacterium acnes. ² This intricate interaction of factors complicates its treatment. ³ The current therapeutic spectrum ranges from topical solutions to oral medications. Primarily, topical retinoids, benzoyl peroxide, and antibiotics are the mainstay of treatment. ¹ In resistant or pronounced cases, oral antibiotics, hormone-regulating treatments, or isotretinoin are used. ⁴ Modern advancements have witnessed a surge in alternative treatments such as chemical peels, pore extractions, and light-based devices for acne management. ⁵

In an effort to avoid systemic therapies, there is a growing interest in light and laser therapies for acne vulgaris treatment. ⁶ Light-based therapies for acne operate through 3 main mechanisms: photochemical effects, photothermal effects, and a combination of both. ⁷ Acne-causing bacteria produce porphyrins, which, when exposed to light, trigger a photochemical reaction generating reactive-free radicals toxic to bacteria. ⁸ Conversely, mid-infrared wavelength lasers can induce a photothermal effect that damages sebocytes by heating the water in the skin surrounding the sebaceous glands, leading to their destruction.^9,10

Light therapy in acne treatment utilizes specific wavelengths targeting different acne-causing factors with minimal side effects compared to other treatment modalities. For instance, blue light (407-420 nm) exhibits a bactericidal property against C. acnes, ¹¹ while red light (620-750 nm) has noted anti-inflammatory effects with good skin penetration, including to the sebaceous gland.^8,12

Other light-based approaches, such as photodynamic therapy and pulsed dye lasers, have shown efficacy in improving acne by reducing inflammation and decreasing sebum secretion. ¹³ Photodynamic therapy combines light sources with photosensitizers to treat acne and other dermatological conditions. ¹⁴ In addition, recent developments in 1726 nm laser systems enable selective photothermolysis of sebaceous glands, offering a safe and effective alternative to traditional acne therapies.^15,16

Combinational therapies utilizing a light source alongside conventional topical acne treatments have demonstrated favourable outcomes. For example, the addition of benzoyl peroxide 5% with concomitant intense pulsed light yielded superior results compared to treatment with benzoyl peroxide alone. ¹⁷ Despite the growing appeal of light therapy for acne treatment, rigorous studies are essential to optimize these modalities and validate their efficacy across a broader patient demographic. ¹⁸ Moreover, head-to-head comparisons with traditional acne therapies are necessary.

While advanced laser systems are primarily available in dermatologists’ offices, there is a growing demand for home-based devices to treat dermatologic conditions, including acne. ¹⁹ Given that visible light sources form the foundation of these home-based devices, this article will concentrate solely on visible light sources and will not address laser, intense pulsed light or photodynamic therapy modalities which require photosensitizers.

Methods

This systematic review was conducted in adherence to the Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines.

Study Inclusion Criteria

Eligibility criteria for this review were established using the population, intervention, comparator, outcomes, and study design (PICOS) framework. Studies were included if they met the predetermined criteria:

• Population: Individuals with acne vulgaris of any age and sex.

• Intervention: Photo biomodulation with visible light, excluding lasers, intense pulsed light and photodynamic therapy.

• Comparator: Any other treatment received; we also included studies which reported on patients without a comparator group.

• Outcomes: Severity of cutaneous findings, clinical response.

• Study design: Randomized controlled trials, observational studies: cohort, case-control and cross-sectional, case series.

A literature search was conducted on July 14, 2023, using MEDLINE, Embase, Evidence-Based Medicine Reviews, and PubMed databases using the search terms listed in Supplemental Table 1.

References of included studies were reviewed to ensure relevant studies were captured. Title, abstract, and full-text screening was conducted by 2 reviewers (E.A.A. and S.M.) using Covidence online systematic review software (www.covidence.org). At the full-text screening stage, studies were excluded if they did not meet components of the PICOS eligibility criteria. Any conflicts between reviewers were resolved by consensus. Searches did not include any language or geographical restrictions. The level of evidence for included articles was determined using the Oxford Centre for Evidence-Based Medicine 2011 Levels of Evidence.

Data Extraction

Data extraction was performed by 4 reviewers (E.A.A., S.M., K.R., and J.B.) using a standardized extraction form which included study type, participant characteristics (eg, age, sex), intervention, response (eg, complete, partial, none, and unknown), and follow-up. The extraction tool was continuously modified to ensure capturing of relevant covariates and outcomes of studies.

Data Synthesis

After data collection, it was determined that quantitative evidence synthesis was not feasible due to heterogeneity in study design and data reporting. Where feasible, quantitative analysis was performed. In addition, a descriptive analysis was performed for studies with available outcome data. To facilitate the aggregation of results from studies with diverse outcomes, we categorized the outcomes into 4 groups based on predefined criteria from individual studies: complete response (CR, “total clearance”), partial response (PR, improvement of acne but not full clearance), and no response (NR, unchanged acne), and worsening (WORS, worsened acne). To maintain a focused analysis, we excluded data from green, orange, and yellow light sources, which comprised ~10% of the initial sample from further analysis.

Results

After title and abstract screening of 1103 studies, and full-text review of 80 studies, ultimately 35 studies met inclusion criteria and were summarized in this review, representing 1185 cases of acne vulgaris (Supplemental Figure 1). A majority (69%) of included studies were level 2 evidence, 20% and 11% were level 3 and 4 evidence, respectively. Studies were published between 1997 and 2023 (Supplemental Table 2).

Patient Characteristics

A total of 1185 patients with acne vulgaris from 35 studies were included in the analysis (Supplemental Table 3). According to available data, 63% were female (n = 585/923). The mean age was 23.7 years (range 12-65 years). Of the available data, mild to moderate acne severity was reported for 80% (n = 429/532) of participants. The reported acne lesions were commonly distributed on the face (94%, n = 1039/1105) and trunk (6%, n = 66/1105). Patients had a washout period from topical or oral anti-acne medications. While most of the studies included healthy participants without comorbidities, one participant received concurrent chemotherapy. There were no other concurrent treatments during treatment with visible light. Patient demographics by treatment modality are detailed in Supplemental Table 4.

Treatment

The most commonly reported light sources were blue light (64%, n = 758/1185), a combination of blue and red light (24%, n = 281/1185), and red light (8%, n = 98/1185). Commonly reported dosages were 48 J/cm² for blue light and 96 J/cm² for red light. The average treatment duration per treatment session for blue and red light was 15 and 8 minutes, respectively. The mean number of treatment sessions was 22, with a range from 1 to 112 (n = 1125/1185). The mean treatment duration was 7 weeks (n = 1069/1185). Treatment-related side effects included skin irritation, transient erythema, dryness, exacerbation of lesions, peeling, and hyperpigmentation. During the visible light therapy intervention period, there were no additional concurrent treatments reported.

Treatment Outcomes

Overall, 91% of patients (n = 1078/1185) had partial resolution, while 4% (n = 48/1185) had complete resolution of lesions in response to light therapy. Among the patients who experienced a partial remission of their acne, 46% experienced a reduction of 0% to 50% in their acne lesions, while 33% and 12% experienced reductions of 51% to 74% and 75% to 99%, respectively. In addition, 3% (n = 37/1185) and 2% (n = 22/1185) of participants experienced no response or worsening lesions after light therapy, respectively (Supplemental Table 3). The mean time to outcome assessment was 3 weeks, with a range from 0.5 weeks to 10 weeks (n = 1175/1185).

Blue Light

Blue light was the most common light source (64%, n = 758/1185). Of the available data, the commonly reported dosage was 48 J/cm² (32%, n = 77/242), with a range from 0.6 to 96 J/cm². The most frequently used irradiance was 90 mW/cm² (24%, n = 76/316), with a range from 3.5 to 90 mW/cm². The mean treatment duration per session was 16 minutes (n = 520/758) while the most reported treatment frequency was 2 treatment sessions weekly (74%, n = 521/700). The mean treatment duration was 6 weeks (n = 690/758) with a mean follow-up period of 10 weeks (n = 577/758). A total of 94% (n = 713/758) and 2% (n = 17/757) of participants experienced partial resolution and complete resolution of acne lesions with treatment. Among the patients who experienced a partial remission of their acne, 44% experienced a reduction of 0% to 50% in their acne lesions, while 42% and 9% experienced reductions of 51% to 74% and 75% to 99%, respectively. A total of 1% of participants (n = 12/758) experienced worsening of lesions with blue light therapy. The mean number of treatment sessions was 19, with a range from 4 to 112 (n = 698/758). Total lesion count improved by 43% at week 4 compared to the baseline. The mean time to outcome was 4 weeks, with a range from 1 to 10 weeks (n = 748/758). Minor side effects were reported in 13% of participants treated with blue light. Treatment-related side effects included skin irritation (n = 54), erythema (n = 23), dryness (n = 14), exacerbation of lesions (n = 6), peeling (n = 4), and hyperpigmentation (n = 1).

Blue and Red Light

A total of 24% (n = 281/1185) of participants were treated with a combination of blue and red lights. The most reported dosages for red and blue light were 96 J/cm² (40%, n = 46/116) and 48 J/cm² (40%, n = 46/116), respectively. The most frequently used irradiance was 40 mW/cm² for blue light and 80 mW/cm² for red light. The mean treatment duration per session was 15 minutes (n = 251/281) while the most reported treatment frequency was 2 treatment sessions weekly (32%, n = 46/146). The mean treatment duration was 8 weeks (n = 281/281) with a mean follow-up period of 11 weeks (n = 251/281). A total of 89% (n = 250/281) and 9% (n = 24/281) of participants experienced partial resolution and complete resolution of acne lesions with treatment. Among the patients who experienced a partial remission of their acne, 46% experienced a reduction of 0% to 50% in their acne lesions, while 15% and 28% experienced reductions of 51% to 74% and 75% to 99%, respectively. A total of 2% of participants (n = 5/281) experienced worsening of lesions with blue light therapy. The mean number of treatment sessions was 34, with a range from 8 to 60 (n = 281/281). Average total lesion count improved by 17% at week 2 compared to the baseline. Inflammatory and noninflammatory lesions improved by 49% and 24%, respectively, at week 4 compared to baseline. The mean time to outcome was 2 weeks, with a range from 1 to 10 weeks (n = 251/281). Minor side effects were reported in 26% of participants treated with a combination of blue and red light. Treatment-related side effects included mild dryness (n = 35), erythema (n = 32), exacerbation of lesions (n = 2), facial rash (n = 2), skin irritation (n = 1), and headaches (n = 1).

Discussion

In summary, this systematic review evaluates the treatment outcomes in 1185 individuals with acne vulgaris who received visible light therapy. ²⁰ The majority of participants included in our review had mild to moderate acne. Regarding the distribution of lesions, it was observed that the face was largely affected in most cases. This is in keeping with the epidemiology of acne primarily affecting the face and trunk. ²⁰ Visible light therapy demonstrated improvement in acne lesions in 95% of treated individuals.

Among the interventions examined, blue light was the most utilized, being delivered in more than half of the cases. In our study, blue light therapy exhibited some efficacy, as evidenced by a significant proportion of patients (95%) experiencing a partial clearance of acne lesions and a minimal 2% exhibiting deterioration posttreatment. Our findings are also in keeping with studies that also found a decrease in acne lesions in patients using blue light therapy.^21,22 On average, these patients experienced this outcome within a period of 4 weeks. A more rapid time to resolution has been reported in several reports, including as early as 7 days posttreatment. ²¹ This outcome sets it apart from alternative interventions examined in our study. Furthermore, it was noted that by the fourth week, the total number of lesions decreased by almost half compared to the first measurement. This suggests that blue light therapy provides both rapid and effective ability to reduce lesion count. A minority of patients experienced treatment-related side effects, primarily skin irritation and erythema. Blue light is known to induce dose-dependent pigmentation in individuals with darker skin types. ²³ Compared to current first-line treatments for acne such as benzoyl peroxide and/or topical retinoids, blue light may have fewer adverse events. ²⁴

The juxtaposition of blue and red light presented a captivating aspect in our analysis. Compared to other light sources, the combination of blue and red light had the highest percentage of patients achieving complete resolution of their acne. The synergistic effect of combining the 2 lights may increase their ability to completely resolve acne lesions, as reported by other studies.^25,26 While the concurrent administration of blue and red light resulted in positive results, a notable number of the patients treated by this approach reported mild and transient adverse effects, mainly xerosis and erythema.

Although photobiomodulation using visible light shows promising results, it is not devoid of potential adverse effects. While these were generally of a modest nature and could be reversed, they exhibited variation depending on the specific treatment methods employed. For example, the presence of blue light was found to be correlated with skin irritation and erythema, whereas the simultaneous exposure to blue and red light occasionally resulted in headaches and facial rashes. Light therapy may also trigger acne flare-ups.^27,28 Whether light therapy ultimately leads to acne clearance or flare-up depends on the nature of the lesions and the causative organism, which may not always be C. acnes. ²⁹ Acne flare-ups after light treatment often result from procedures involving ablative lasers. ⁸

Limitations

This review has limitations that may affect the generalizability of its findings. It is worth noting that included trials frequently had limited sample sizes, which may introduce a potential bias in the results or hinder the ability to capture a broader range of patient responses. Furthermore, the reviewed studies lacked comparisons between light therapy and various multimodal treatments for acne. Such an omission restricts our understanding of light therapy’s relative efficacy in managing acne. Moreover, the diverse treatment outcomes that have been reported, along with the utilization of different scales, have posed a significant challenge in synthesizing the findings into cohesive conclusions. Another limitation is to the lack of consistent outcome measures to evaluate the severity of acne in patients categorized broadly as having mild to severe conditions. The lack of standardized assessment methods adds more complexity to the task of comparing outcomes across different studies. Furthermore, many included studies failed to include crucial factors, such as dosage, mean power, and proximity to light, thereby compromising the capacity to reproduce these experiments. Moreover, we did not include studies where light therapy is combined with topical therapy. Finally, it should be noted that although there was some provision of information pertaining to side effects, there were several cases where the specific quantity of patients affected by each adverse event was not explicitly outlined.

Conclusion

Visible light therapy may be an effective, safe, and noninvasive treatment for acne vulgaris. The majority of patients with mild to moderate acne receiving 3 or more treatment sessions reported some improvement in their acne in 4 weeks. Additional research is needed to assess the long-term effectiveness of light therapy for acne vulgaris and potential utilization both in clinical settings and as at-home therapies. More importantly, head-to-head studies are needed to evaluate the efficacy of visible light compared to existing therapies for the treatment of acne.