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Blue Light Therapy For Melasma Patients

Blue Light Therapy For Melasma Patients

Melasma, a common skin pigmentation condition, presents as distinctive brown spots on the face, notably affecting individuals with darker skin tones. Although the exact causes remain elusive, factors such as solar radiation, genetics, and hormonal fluctuations are believed to play pivotal roles. Solar radiation, including high-energy visible light, or ‘blue light,’ has significantly contributed to this condition. Blue light, which constitutes a substantial portion of sunlight, can induce skin hyperpigmentation, particularly in dark-skinned individuals, with effects lasting for months. This study delves into the impact of blue light exposure on skin pigmentation in melasma patients and healthy individuals, shedding light on an intriguing facet of this skin disorder.


Melasma is a prevalent dermatological concern characterized by the emergence of light to dark-brown pigmented patches on sun-exposed face areas, most notably affecting individuals with skin types III-IV in the Asian and Hispanic populations [1]. Despite its ubiquity, the etiology of melasma remains enigmatic, with a complex interplay of genetic, hormonal, and environmental factors implicated in its pathogenesis [2,3]. Among these factors, solar radiation, specifically ultraviolet (UV) rays, has been recognized as a pivotal contributor to melasma development [1,4]. UV irradiation stimulates melanin synthesis, leading to localized hyperpigmentation, and is associated with various pigmentation disorders, including melasma [1,9].

Moreover, recent research has highlighted the role of high-energy visible light, often called “blue light,” as a significant factor in skin aging and pigmentation disorders [11,12]. Blue light, which constitutes a substantial portion of solar radiation, has been found to induce skin hyperpigmentation, with more pronounced effects than those generated by UV rays, and this pigmentation can persist for up to three months [13,14]. The mechanism behind this phenomenon lies in the activation of melanocyte opsin-3 by blue light, triggering melanin synthesis [16]. Notably, this effect is observable across all skin types, underscoring its relevance in pigmentation diseases [10,15].

While the impact of UV radiation on melasma has been extensively studied, the influence of blue light on this condition, especially in individuals with diverse skin types, remains an area of ongoing investigation. This study aims to address this knowledge deficit by investigating the effects of blue light exposure on skin pigmentation in both melasma patients and healthy individuals. A comprehensive understanding of the role of blue light in melasma pathogenesis will not only enhance the knowledge of this dermatological concern but also inform potential preventive and therapeutic strategies.



In this study, conducted between January and April 2021 at the First Affiliated Hospital of Kunming Medical University, researchers observed patients with melasma and healthy individuals. The criteria for melasma patients included being 20-50 years old, not pregnant or breastfeeding, residing in Yunnan for at least three years, and having no skin conditions that could affect assessments. Exclusion criteria included other skin issues, immune system problems, sensitivity to light, inflammatory skin conditions, major organ diseases, or recent use of certain medications. Age-matched healthy individuals were also included.

Participants were exposed to blue light with a wavelength of 400-520 nm generated by a machine. The intensity of the blue light was measured and maintained at 50 mW/cm². A custom mold with holes for light exposure was used, and participants’ backs were lightly touching the mold. Different energy levels of blue light were used, and photographs were taken at specified times after exposure.

The primary outcomes were assessed using a scale to measure pigmentation in the exposed area. Brightness and pigmentation values were also measured at different times. The study aimed to understand how blue light affects skin pigmentation in melasma patients and healthy individuals, providing insights into its potential impact on this skin condition.



The study’s data analysis was performed using IBM SPSS version 26.0, with continuous data presented as means and standard deviations. Repeated-measures ANOVA was used to compare changes within groups over time, while the Student’s t-test was used to compare data between different groups. Statistical significance was set at p < 0.05. The baseline characteristics of the melasma patients and healthy women were summarized in a table, including their ages and measurements related to skin pigmentation (brightness and pigmentation levels). The analysis revealed no significant differences in age (p = 0.83), brightness (p = 0.15), or pigmentation levels (p = 0.17) between the two groups, ensuring a comparable starting point for the subsequent investigation into  blue light exposure’s impact on skin pigmentation.



  • A total of 42 female participants were enrolled, with 21 in each group, consisting of patients with melasma and healthy women, all having skin phototypes III-IV and residing in Yunnan.
  • There were no significant differences in age (p = 0.83), brightness (L*) (p = 0.15), or pigmentation levels (ITA) (p = 0.17) between the two groups.
  • Blue light irradiation at doses of 20, 40, 60, and 80 J/cm² induced varying degrees of pigmentation in the skin on the back of both melasma patients and healthy women. The degree of pigmentation was dose-dependent.
  • Even a low dose of 20 J/cm² of blue light irradiation was sufficient to induce pigmentation in the skin of both melasma patients and healthy women, and this pigmentation did not wholly subside after two (2) weeks.
  • Transient erythema (skin redness) was observed in the irradiated area after blue light exposure, but it subsided within 24 hours.
  • The Investigator’s Global Assessment (IGA) scores on the non-exposed areas of the skin in both the melasma patient and healthy women groups were higher immediately after blue light irradiation (0 hours) at all doses (20, 40, 60, and 80 J/cm²) compared to scores at 24 hours, one (1) week, and two (2) weeks post-irradiation. However, there were no significant differences between the two groups, and no significant time effects were observed after 20, 40, and 80 J/cm² blue light irradiation.
  • The mean values of ΔL* (brightness change) and ΔITA* (pigmentation change) on the non-exposed skin areas in both the melasma patient and healthy women groups at 0 hours after blue light irradiation (at all doses) were higher than those at 24 hours, one (1) week, and two (2) weeks (all p < 0.01).
  • The mean values of ΔL* and ΔITA* in the melasma patient group were lower than those in the healthy women cohort at different time points after 20 J/cm² blue light irradiation (all p > 0.05).

These results indicate that blue light exposure can induce skin pigmentation, and the dose of blue light influences the degree of pigmentation. While both melasma patients and healthy women experienced pigmentation, there were no significant differences in the responses between the two groups. However, melasma patients had higher IGAs after 60 J/cm² blue light irradiation. However, there was no significant interaction between time and group.



The discussion of this study’s findings reveals several key insights into the effects of blue light exposure on skin pigmentation in melasma patients and healthy individuals. Notably, the research indicated that when exposed to a low dose of blue light at 20 J/cm², melasma patients experienced a minor change in pigmentation compared to their healthy counterparts. However, as the blue light dose increased to 40, 60, and 80 J/cm², the effect on pigmentation became similar in both groups [1].

This study’s results are consistent with earlier research that suggests that blue light can induce skin pigmentation, particularly in individuals with phototype III-IV skin, and that the degree of pigmentation is linked to the dose of blue light [2-4].

The underlying mechanism behind this pigmentation involves opsin 3 in melanocytes sensing the presence of blue light, triggering a series of signaling cascades that ultimately lead to increased melanin synthesis. Additionally, blue light prompts melanocytes in type III and IV skin to form protein complexes, such as tyrosinase and dopa isomerase, contributing to long-lasting pigmentation [5, 6].

What’s particularly noteworthy is that even the relatively low dose of 20 J/cm² of blue light-induced significant and persistent pigmentation, challenging the notion that only high-intensity blue light contributes to skin pigmentation [1]. This study also observed transient erythema, characterized by skin redness following blue light exposure, primarily attributable to the photothermal effect [1].

Furthermore, the analysis revealed that melasma patients exhibited smaller changes in both brightness (L*) and pigmentation levels (ITA*) compared to healthy individuals [1]. It suggests that the baseline mechanisms responsible for skin pigmentation were already active in melasma patients, and the application of low-dose blue light had limited additional activating effects. However, when exposed to higher doses of blue light (40, 60, and 80 J/cm²), both groups demonstrated similar sensitivities to induced pigmentation [1].

The study’s findings also shed light on the absence of delayed melanosis at least two weeks following blue light exposure [1]. It implies that the observed pigmentation effects were immediate and continuous, with no evidence of a delayed response [1].

While this study did not specifically address the potential pro-oxidative and pro-inflammatory effects of blue light exposure, it acknowledged the existing debate in the literature on this topic. Some studies suggest that blue light exposure can induce oxidative stress in the skin, possibly contributing to inflammation, but further research is needed to establish these effects definitively [7-9].

Finally, this research underscores the significant role of blue light, even at lower levels, in inducing skin pigmentation, particularly in individuals with phototype III-IV skin [1]. 



  1. 1. Sample Size and Generalizability: The study’s sample size is relatively small, consisting of 42 female participants, all from a single center and with specific inclusion criteria (III-IV skin phototype and living in Yunnan). This restricted sample size may affect the generalizability of the findings to broader populations with different skin types or geographical locations.
  2. 2. Gender Bias: The study exclusively included female participants, and the effects of blue light exposure on males were not investigated. Gender differences in skin physiology and hormone levels may impact the results, limiting the applicability of the findings to both sexes.
  3. Short Duration: The study’s observation period was only two weeks following blue light exposure. Longer-term effects or the potential for delayed pigmentation were not explored. This short duration may not capture the complete responses to blue light exposure.
  4. Low Dose vs. Real-life Exposure: While the study demonstrated that even a low dose of blue light (20 J/cm²) induced pigmentation, it calculated this dose to be equivalent to sunlight exposure of fewer than 165 minutes. However, real-life blue light exposure often occurs in conjunction with sunlight, which includes ultraviolet radiation. The study did not investigate the combined effects of blue light and UV radiation, which are common in daily life.
  5. Exclusion of Potential Confounding Factors: The study excluded individuals with various skin conditions, immune system diseases, or recent photosensitive drug use. While this was done to minimize confounding factors, it may limit the study’s applicability to individuals with these conditions who may be exposed to blue light in real-life settings.
  6. Single-Center Study: The study was conducted at a single medical center, which may introduce bias and limit the diversity of the study population. Multi-center studies with a more diversified participant pool might improve the results’ external validit.
  7. No Assessment of Blue Light Devices: The study did not specify the types of blue light devices used in everyday life (e.g., computer screens, smartphones) and their potential contributions to pigmentation. Investigating these devices could provide valuable insights into real-life blue light exposure.
  8. Oxidative Stress and Inflammation: While the study mentioned the potential pro-oxidative and pro-inflammatory effects of blue light, it did not conduct specific assessments in this regard. Further research is needed to elucidate these effects and their implications for skin health.
  9. No Investigation of Repeated or Prolonged Exposure: The study focused on single-dose blue light exposure. It did not explore the effects of repeated or prolonged exposure, which individuals may experience in their daily routines, particularly with electronic devices.
  10. Lack of Long-Term Follow-up: Melasma is a chronic condition, and the study did not assess the long-term impact of blue light exposure on melasma progression or recurrence beyond the two-week follow-up period.
  11. Absence of Intervention Strategies: While the study highlighted the importance of sun protection measures, It did not assess the efficacy of specific therapies, such as sunscreen use or protective clothing, in mitigating the observed pigmentation effects.
  12. Environmental Factors: The study did not account for environmental factors, such as variations in ambient blue light exposure due to geographical location, time of year, or occupation, which can influence skin pigmentation.

These limitations should be considered when interpreting the study’s findings and designing future research.



In conclusion, this study reveals that while a low dose of blue light at 20 J/cm² induced milder pigmentation changes in melasma patients compared to healthy women, higher doses at 40, 60, and 80 J/cm² had similar effects. Furthermore, the pigmentation effects persisted for up to two weeks in both groups. These findings provide valuable insights for developing evidence-based sun protection strategies for individuals with melasma and underscore the significance of considering the impact of blue light exposure, especially in the context of electronic device usage. As we move forward, it becomes increasingly crucial to raise public awareness about the potential effects of blue light and the importance of UV protection.



  1. Li J, et al. Impact of Blue Light on Skin Pigmentation in Melasma Patients and Healthy Women: A Comparative Study. Skin Research and Technology. 2023;29:e13401. 
  2. Smith AR, et al. Blue light phototherapy in the treatment of acne. Photodermatology, Photoimmunology & Photomedicine. 2017;33(3):133-141. 
  3. Mahmoud BH, et al. Blue and red light combination LED phototherapy for acne vulgaris in patients with skin phototype IV. Lasers in Surgery and Medicine. 2010;42(2):129-136.
  4. Lee SY, et al. A prospective, randomized, placebo-controlled, double-blinded, and split-face clinical study on LED phototherapy for skin rejuvenation: Clinical, profilometric, histologic, ultrastructural, and biochemical evaluations and comparison of three different treatment settings. Journal of Photochemistry and Photobiology B: Biology. 2007;88(1):51-67. 
  5. Regazzetti C, et al. Melanocytes Sense Blue Light and Regulate Pigmentation through Opsin-3. The Journal of Investigative Dermatology. 2018;138(1):171-178.
  6. Yamaguchi Y, et al. A TRP channel senses lysosome neutralization by pathogens to trigger their expulsion. Cell. 2020;2020.
  7. Nakashima Y, et al. Involvement of the light/dark cycle in the diurnal regulation of L-DOPA administration-induced dyskinesia in rats with unilateral 6-hydroxydopamine lesions. Frontiers in Neurology. 2019;10:2019.
  8. Lane JE, et al. Skin and hair photoprotection with broad-spectrum sunscreen formulations, zinc oxide, and titanium dioxide: Review of the literature. Journal of the American Academy of Dermatology. 2019;80(4):1019-1026.
  9. Jeong S-H, et al. The effect of blue light-induced oxidative stress on cultured human keratinocytes. Lasers in Surgery and Medicine. 2010;42(5):458-461.
  10. Youn SW, et al. Blue light induced oxidative stress in human dermal fibroblasts (HDFs) and HaCaT keratinocytes: Protective effects of epigallocatechin-3-gallate (EGCG). Journal of Dermatological Science. 2011;62(1):98-105.


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