Efficacy and Safety of the 1,320-nm Nd:YAG Laser in the Treatment of Acne Vulgaris: A Retrospective Study

Dear Editor:

Acne vulgaris is a chronic inflammatory disease of the pilosebaceous unit, presenting as inflammatory or non-inflammatory lesions¹. Various laser therapies have been explored as treatment options for acne vulgaris²,³,⁴,⁵. Among these, the 1,320-nm Nd:YAG laser has attracted interest due to its deeper dermal penetration and potential effects on sebaceous gland activity. Although some studies on 1,320-nm laser have reported longitudinal changes in acne-related parameters, objective assessments of sebum and porphyrin remain limited. Therefore, this study aimed to evaluate the efficacy and safety of the 1,320-nm Nd:YAG laser treatment, incorporating sebum and porphyrin as additional parameters to characterize treatment-related changes in acne.

A total of 40 Korean patients (26 females and 14 males; age range, 18–56 years) treated at Renewme Dermatologic Clinic between November 2023 and November 2024 were retrospectively enrolled. Eligible participants were adults who had received at least 5 weekly sessions of 1,320-nm Nd:YAG (Eravity; Innomed, Seoul, Korea) laser treatment. Patients who received other laser treatments, systemic medications, or additional procedures that could affect acne outcomes during the study period were excluded; however, prior treatment history and washout periods were not standardized.

The 1,320-nm Nd:YAG laser was generally administered using more than 20 passes per session (for about 20 minutes) with a wavelength of 1,320 nm (40 Hz, 650 μs, 10 W), a fluence of 0.5 J/cm² and an 8-mm spot size. Standardized facial photographs were obtained at week 0 (Visit 1), week 3 (Visit 2), and week 5 (Visit 3) using a specialized diagnostic imaging system (MarkVu; PSI Plus, Suwon, Korea). Inflammatory and non-inflammatory lesion counts as well as sebum and porphyrin levels were assessed from the images. Sebum and porphyrin were evaluated on fluorescence signals, providing semi-quantitative estimates. Acne severity was assessed using the Investigator’s Global Assessment (IGA). Changes over time were analyzed using repeated-measures analysis of variance and the Friedman test, with statistical significance at p<0.05 (SPSS version 27.0; IBM Corp., Armonk, NY, USA).

This study was approved by the Institutional Review Board (IRB) of Kyung Hee University Hospital (IRB No. 2026-01-109) and conducted in accordance with the principles of the Declaration of Helsinki. Written informed consent was obtained from all participants.

Demographic characteristics of the 40 patients are presented in Supplementary Table 1. Inflammatory lesion counts significantly decreased over time (29.15 at baseline to 13.58 at week 5, p=0.003) (Table 1). Non-inflammatory lesions showed a delayed but significant reduction by week 5 (22.00 at baseline to 19.03 at week 5, p=0.030). Sebum levels also significantly decreased (16.23 at baseline to 8.83 at week 5, p=0.045), whereas porphyrin levels did not show a significant overall reduction (p=0.150). Acne severity, assessed by IGA, significantly improved over time (p=0.014). A representative case demonstrating clinical improvement over time is shown in Fig. 1. Post hoc analyses were consistent with these results (Supplementary Table 2).

Table 1. Comparison of acne-related metrics across visits.

Outcomes	Visit 1 (baseline)	Visit 2 (week 3)	Visit 3 (week 5)	p-value
Inflammatory lesion count	29.15±17.83	19.68±15.80	13.58±14.19	0.003
Non-inflammatory lesion count	22.00±14.80	23.20±13.15	19.03±11.70	0.030
Sebum	16.23±9.70	12.10±7.04	8.83±6.36	0.045
Porphyrin	16.68±10.52	14.45±8.60	12.35±7.80	0.150
IGA	3.70±0.82	3.35±0.86	2.78±0.77	0.014

Values are presented as mean ± standard deviation.

IGA: Investigator’s Global Assessment.

Fig. 1. Patients treated with a 1,320-nm Nd:YAG laser. (A) Before the first treatment, (B) 3 weeks after the first visit and (C) 5 weeks after the first visit. As treatment progresses, improvements in inflammatory acne lesions can be clearly observed.

Patients were categorized into mild (IGA ≤2), moderate (IGA=3), and severe (IGA ≥4) groups based on their IGA scores. Subgroup analysis demonstrated that, in the severe group, most metrics consistently decreased over time (Supplementary Table 3). In the moderate group, similar improvements were observed. Due to the small sample size, the mild group was not analyzed.

Treatment was well tolerated. Mild transient erythema and a burning sensation were observed, resolving spontaneously within 1–2 hours, with no persistent adverse events reported during follow-up.

This study demonstrated that 1,320-nm Nd:YAG laser may be a useful option for treating acne vulgaris, showing substantial reductions in inflammatory lesions, sebum, and overall acne severity. These findings are consistent with previous studies, reporting the efficacy of the 1,320-nm laser treatment in acne⁴,⁵. In addition to confirming these results, the present study incorporated sebum and porphyrin as additional parameters, allowing assessment of treatment-related changes beyond lesion counts.

The observed reduction in sebum levels may be explained by the photothermal effects of the 1,320-nm Nd:YAG laser, which induce dermal heating and may lead to functional modulation of sebaceous gland activity⁴,⁶. Although porphyrin levels did not show a significant reduction in the overall cohort, significant reductions were observed in patients with moderate-to-severe acne, suggesting an indirect antimicrobial effect in those with a greater inflammatory burden. These findings suggest that the primary mechanism of action may involve modulation of sebaceous gland activity, while an indirect antimicrobial effect through alteration of the follicular environment may also contribute to the observed clinical improvement. However, some studies revealed that most structural alterations in sebaceous glands following laser treatment are transient⁷,⁸. Further investigations are needed to understand the impact of 1,320-nm Nd:YAG laser on sebaceous glands.

Although the relatively short follow-up period of the study may have contributed to this finding, the overall tolerability of the laser treatment was favorable. The laser device used in this study has a relatively short pulse duration (650 μs), which may contribute to reduced discomfort and downtime compared with longer-pulse systems, possibly due to limited heat diffusion to surrounding tissues. This favorable safety profile may, at least in part, be attributable to the shorter pulse duration, and no active pain control measures were required during treatment.

There are several limitations in this study. The observation period was relatively short, making it difficult to assess the long-term efficacy and safety of the 1,320-nm Nd:YAG laser. Additionally, the sample size was small, and no control or comparative treatment group was included, which limits generalizability and precludes conclusions regarding comparative effectiveness. Furthermore, prior treatment history and washout periods were not standardized due to the retrospective design, and potential carry-over effects cannot be excluded. Future studies with larger sample sizes, randomized controlled designs, longer follow-up periods, and comparative groups are needed to confirm the results and establish the clinical significance of the 1,320-nm laser in acne treatment.

In conclusion, 1,320-nm Nd:YAG laser treatment was associated with improvements in inflammatory lesions, sebum levels, and overall acne activity. These findings suggest that the treatment may modulate sebaceous gland activity. Further prospective studies are warranted to clarify the long-term efficacy and underlying mechanisms of this approach.

SUPPLEMENTARY MATERIALS

Supplementary Table 1

Demographic profile of participants

Supplementary Table 2

Post hoc analysis between visits for each metric

Supplementary Table 3

Changes in acne-related metrics within subgroups based on acne severity