Objective To study the effects of light damages of epidermal permeability barrier on cosmetics function evalu-ation.Methods 10volunteers were selected during the1st stage i.e.the3-month experiment of cosmetics function carried out using the traditional method.The skin moisture,transepidermal water loss and skin elasticity were measured,and the required sample size was estimated also.The2nd stage of the experiment of cosmetics function was carried out based on the data of the1st stage.The skin surface was cleaned with the detergent containing sodium lauryl sulfate with mass fraction of5%to induce light damages in skin surface before testing with cosmetics every day,those indexes mentioned above were measured also.Re -sults The1st stage of the experiment using the traditional evaluation method showed that the skin moisture,transepidermal wa-ter loss and skin elasticity revealed significant differences in the3rd month after testing with cosmetics compared with those be-fore testing with out cosmetics(P