Exposure to harsh environmental conditions, such as cold and dry climate and chemicals can have an abrasive effect on skin. Skin care products containing ingredients that avert these noxious effects by reinforcement of the barrier function can be tested using in vivo models. The objective is to use in vivo models to assess the efficacy of emollients in protecting skin against climatic and chemical insults. A first model used a stream of cooled air to mimic cold wind. A second used sodium lauryl sulfate (SLS) under patch as chemical aggressor. In the model with simulated wind exposure, the untreated exposed area had a significant decrease in hydration. In contrast, application of an emollient caused a significant increase in hydration that was maintained after wind exposure. In the second model with SLS exposure, application of a barrier cream before SLS patch significantly reduced the dehydrating effect of SLS with a significant difference in variation between both areas. Application of the cream reduced TEWL, indicative of a physical reinforcement of the skin barrier. The two presented test methods, done under standardized conditions, can be used for evaluation of protective effect of emollient, by reinforcing the barrier function against experimentally induced skin dehydration. 1. Introduction The skin is the outermost barrier that protects the human body from physical, chemical, and microbial insults and prevents the uncontrolled loss of water among other substances. The epidermal barrier function of the skin resides in the stratum corneum (SC) and is linked to the protein-enriched corneocyte layers and the intercellular membrane lipids mostly composed of ceramides, cholesterol, and free fatty acids [1, 2]. Corneocytes are rapidly and continually replaced to maintain skin integrity and to repair damage. Exposure to external factors can damage this protective function. Much studied is the cumulative damage of sun exposure as it accounts to a great extent for the permanent changes in skin physiology and morphology over time [3]. Other environmental aggressors that significantly impact on skin properties and may cause acute or chronic damage of the skin barrier include climatic conditions (e.g., wind, low temperatures, low humidity) and chemicals in frequent contact with the skin (e.g., soaps and detergents) [4, 5]. Exposure to such aggressors can reduce the hydration status of the epidermis and compromise the skin barrier function. Skin dryness reflects an abnormal desquamation process, where corneocytes are shed as visible scales, causing the
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