Disparity in cutaneous pigmentary response to LED vs halogen incandescent visible light: Results from a single center, investigational clinical trial determining a minimal pigmentary visible light dose

Background: While most of the attention regarding skin pigmentatiorHias focused on the effects of ultraviolet radiation, the cutaneous effects of visible light (400 to 700nm) are rarelyNreported. Objective: The purpose of this study was to investigate the cutaneous pigmentary response to pure visible light irradiation, examine the difference in response to different sources of visible light irradiation, and determine a minimal pigmentary dose of visible light irradiation in melanocompetent subjects with Fitzpatrick skkjtype III - VI. Methods: The study was designed as a single arm, non-blinded, split-side dual interventiorKstudy in which subjects underwent visible light irradiation using LED and halogen incandescent light sources delivered at a fluence of 0.14 Watts/cm2 with incremental dose progression from 20 J/cm2 to 320 J/cm2 Pigmentation was assessed by clinical examination, cross-polarized digital photography, and analytic coterimetry. Results: Immediate, dose-responsive pigment darkening was seen with LED light exposure in 80% of subjects, beginning at 60 Joules. No pigmentary changes were seen with halogen incandescent light exposure at any dose in any subject. Conclusion: This study is the first to report a distinct difference in cutaneous pigmentary response to different sources of visible light, and the first to demonstrate cutaneous pigment darkening from visible LED light exposure. Our findings raise the concern that our increasing daily artificial light surroundings may have clandestine effects on skin biology.