Effects of pH Differences on the Skin Moisturizing Capacity of Natural Moisturzing Factors

Pyo, Hyung Chan; Kim, Hong Jig; Kim, Young Keun

Abstract

The flexibility of surface layer of skin is largely dependent upon the layer's water content. This, in turn, depends primarily on the quantity of water soluble hygroscopic and surface active msterials within the straturn corneum, often known as the natural moisturizing fsctors(NMF). It consist of amino acid, lactic acid, pyrrolidone carboxylic acid and inorganic salts etc.. Some of these components are greatly influenced by hydrogen ion content and ionic form of them were found to be highly hygroscopic. In this experiment, sunburn exfoliated human stratum corneum and pig epidermis separated by 2N-NaBr were used as in vitro test. These tissues were so treated to hsve each pH value (3, 5, 7, 9) and their water holding capacity and hygroscopicity were measured by gravimetric method. The results are summarized as follows : 1, Water holding capactiy of sunburn exfoliated human skin showed significant increase at pH 5 (p<0.1), 7 (p<0.01), 9 (p<0.01) compared to pH 3, and increase in pH 7 (p<0.1), 9 (p<0.05) compared to pH 5 in lactic acid. In pig epidermis, there was significant increase at pH 5 (p<0.05), 7 (p<0.01), 9 (p<0.05) cornpared to pH 3 in lactic acid. 2. Hygroscopicity of pig epidermis showed significant increase at pH 5 (p<0.05), 7 (p<0.1), 9 (p<0.05) in lactic acid and at pH 5