Abstract
Recently, the number of female consumers who recognize their own sensitive skin is increasing, and the cosmetic market for such consumers is also spreading. Since no in vitro method of testing safety for sensitive skin cosmetics has existed, safety tests have been performed with sensitive skin subjects. Therefore establishment of in vitro methods for sensitive skin cosmetics is desired. From the point of view of animal welfare, the cosmetic industries have used alternative methods without animal use increasingly. For these reasons, we tested a 13-day or 6-day cultured reconstructed human epidermal model, LabCyte EPI-MODEL, to clarify whether these skin models are suitable as tools for the safety tests targeted for sensitive skin, focusing on the loss of skin barrier function, one of the characteristics of sensitive skin. We confirmed that 6-day cultured models had thinner stratum corneum, a lower amount of ceramide contents and higher TEWL values than 13-day cultured models. Based on the results of the in vitro skin irritation tests, 6-day cultured models, which had immature stratum corneum, showed higher sensitivity to most chemicals or cosmetics than 13-day cultured models. Furthermore, we confirmed that longer exposure of substances on 6-day cultured models made the results more clear. These findings indicate that, using 6-day cultured LabCyte EPI-MODEL, we can evaluate the potential skin irritation levels of chemicals and cosmetics, and suggest the possibility that the model is one of the safety evaluation tools to develop cosmetics for sensitive skin.
