752 Clinical effects of LED blue light on skin pigmentation and carotenoid depletion

Abstract

The growing evidence that visible light - and especially blue light - contributes to detrimental effects of sun exposure to skin, is becoming a subject of controversial debate nowadays. In this study we aimed to assess blue light-induced pigmentation and carotenoid depletion in vivo. Furthermore, we wanted to show a protective effect of SPF50 sunscreen formulations in a double-blind, placebo-controlled trial. The UVA/B filter system included the microfine particles titanium dioxide and methylene bis-benzotriazolyl tetramethylbutylphenol that extend effectiveness into the blue light range. Comparisons between repetitive irradiation with LED blue light (450 ± 20 nm) with 45 J/cm2 over 5 consecutive days after daily product application (2 mg/cm2) and irradiation only once with 135 J/cm2 after product application over 6 days were performed on the back of the volunteers. The extent of pigmentation and carotenoid depletion was investigated with the assessment of the skin color (ITA°) by chromameter measurements and the in vivo carotenoid concentration via multiple spatially resolved reflectance spectroscopy, respectively. Assessments were performed 5 hours, 24 hours, 1 week and 2 weeks after the last irradiation. Fourteen subjects terminated the study. Both, the single high-dose and the repetitive exposure resulted in comparable, immediate (≤ 5h) increase of skin pigmentation and carotenoid degradation (p<0.001). Skin pigmentation and carotenoid depletion attenuated on all test conditions already one day after the last irradiation. Both effects were still evident one and two weeks after the last irradiation. The application of the cosmetic formulations including UV pigments that scatter in the blue light range significantly reduced pigmentation (p<0.001) right after irradiation that might be considered for holistic light protection beyond UV.