Dose dependent sun protective effect of topical melatonin: A randomized, placebo-controlled, double-blind study

Background: Ultraviolet radiation (UVR) by sul - l>nlight results in an increasing number of skin conditions. Earlier studies have suggested a protective effect of topical treatment with the pineal hormone melatonin. However, this protective effect has never been evaluated in natural sunlight, and the optimal dosing has not been clarified. Objective: The aim of this study was to investigate the sun protective effect of topical treatment with three different doses of melatonin (0.5%, 2.5%, 12.5%) against erythema induced by natural sunlight. Method: The study was a randomized, placebo-controlled, double-blind study in healthy volunteers. Twenty-three healthy volunteers, 8 male and 15 female, were enrolled. The protective effect of three different doses of melatonin cream (0.5%, 2.5%, 12.5%) against erythema induced by natural sunlight was tested. All participants had their backs exposed to sun from 1:22 PM to 2:02 PM local time and UV-index was 9. Primary outcome was reduction in erythema evaluated by chromatography after sun exposure, when treated with topical melatonin cream (0.5%, 2.5%, 12.5%) versus placebo and no treatment. The erythema reaction was evaluated with chromatography and visual scoring at baseline, one, four, eight and 24 h after exposure. Results: Significant difference in erythema formation was found between areas treated with melatonin cream 12.5% and areas receiving placebo or no treatment (repeated measures ANOVA p = 0.001). No differences were found between placebo and the 0.5% and 2.5% concentrations. Conclusion: Application of melatonin cream 12.5% protects against natural sunlight induced erythema. (C) 2016 Japanese Society for Investigative Dermatology. Published by Elsevier Ireland Ltd. All rights reserved.