Blenkiron1, P., Betteridge1, J., Vanoosthuyze1, K., Flood2, J. 1P&G Beauty, Egham, United Kingdom; 2P&G Beauty, Cincinnati, OH, United States.

The destructive role of free radicals in biological systems is well recognised and is manifested most commonly in ultraviolet (UV) light-induced skin damage, so-called photoaging. Sources of free radicals or reactive oxygen species (ROS) include not only UV from sunlight but also other environmental stresses, such as ozone or smog. We present data showing how antioxidant-containing cosmetic formulations can visually inhibit free radical formation in skin. Objective:  Determine the effect of topically applied antioxidant formulations on the inhibition of free radical formation under conditions of oxidative stress. Methods: Living Skin Equivalents (Epiderm 200, MatTek) were separately treated with full formulation and vehicle control (minus the antioxidant package), then doped with dihydrorhodamine reagent (radical visualisation tag). Samples were then exposed to UVA-UVB or ozone as a ROS source and imaged using a 2-photon fluorescence microscope. Results: Coloured intensity maps of ROS in skin tissue were generated for each sample. Fluorescence signals were used to calculate the percent quenching of ROS by each formulation relative to the placebo. In this study, a full formulation sample (with antioxidants) was found to inhibit ROS formation in tissue by 33% vs. a noantioxidant control (P < .05). In this paper we will further describe the use of alternative stress sources (ozone, smog, and automotive pollution) and their utility in screening effective antioxidant agents.

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