THE INFLUENCE OF COSMETIC PRODUCTS ON THE STRATUM CORNEUM BY INFRARED AND RAMAN SPECTROSCOPY.
The stratum corneum is the outermost layer of the skin and as such represents the decisive barrier between the body and the environment. The combination of horny cells and lamellar lipid layers prevents water loss from the body and protects it against penetration by exogenous substances. For selective investigation of the thin outermost stratum corneum layer, ATR-FTIR (attenuated-total-reflection-Fourier-transform-infrared) spectroscopy has proved itself in practice. It provides information about the sebum content, type of fatty substances, water content and degree of order of the lamellar lipid film in the stratum corneum. Complementary information is obtained by NIR-FT-Raman (near-infrared-Fourier-transform-Raman) spectroscopy, which is shown in comparison to infrared spectroscopy by scrutinizing in-vitro epidermis and full-skin models. In cleansing processes a large part of the sebum is removed from the skin. The skin reacts to the de-fatting process by the rapid secretion of sebum. Cleansing with a mild facial cleansing emulsion de-fats the skin less than a surfactant shower gel. Skin creams cause alterations to the skin moisture and in the degree of order of the stratum corneum lipids. A lamellar cream with a structure similar to, but not identical to, that of the stratum corneum lipids increases the degree of order of the alkyl chains of the skin lipid film (biomimetic principle) while a conventional w/o cream reduces this degree of order Skin moisture increases after the use of the creams.
ATR-FTIR, Barrier properties formation, Cosmetic products, EpiDerm, Ex-vivo skin, FTIR, Infrared, Lamellar, NIR-FT, NIR-FT-Raman, Profiles/Analyses, Raman, Sebum, Stratum corneum, Water-in-oil
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