Effect of topical antioxidants on UV-induced erythema formation when administered after exposure

Background: Photoprotective effects of topically applied antioxidants when applied before ultraviolet radiation (UVR) exposure are well known. Their p rotective effect when applied after UVR exposure is, however, less establis hed. Objective: In a randomized, double-blinded, placebo-controlled human s tudy the short-term photoprotective effects of different antioxidants and o f their combinations were evaluated when applied after UVR exposure, Method s: Melatonin (N-acetyl-5-methoxytryptamine), vitamin E (alpha-tocopherol) a nd vitamin C (ascorbic acid) were topically administered alone or in combin ation following UVR exposure as single applications (immediately or 30 min after irradiation, respectively) or as multiple applications (three times: 30 min, ? h and 2 h after irradiation). The erythema[ reaction was evaluate d visually and noninvasively with bioengineering methods (skin color and sk in blood flow). Results: No significant protective effect of melatonin or the vitamins when applied alone or in combination were obtained when antioxidants were appli ed after UVR exposure. No improved photoprotective effect was obtained when multiple applications were done. Conclusion: UVR-induced skin damage is a rapid event, and antioxidants poss ibly prevent such damage only when present in relevant concentration at the site of action beginning and during oxidative stress.