Henkel KGaA, Düsseldorf, Germany.
Int J Cosmet Sci. 2000 Oct;22(5):371-83. doi: 10.1046/j.1467-2494.2000.00028.x.
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. Different types of skin (dry, normal and greasy) differ mainly in their sebum content but also in the composition of their fats and the degree of order of their lipids. A comparison with model lipid mixtures shows that the stratum corneum lipids are mainly present in a fixed gel form under physiological conditions. In cleansing processes a large part of the sebum is removed from the skin. The skin reacts to the defatting process by the rapid secretion of sebum. After cleansing with a mild face cleansing emulsion the re-achievement of the same fat status takes longer than with 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 that of the stratum corneum lipids increases the degree of order of the alkyl chains of the skin lipid film (biomimetic principle), whereas a conventional w/o cream reduces this degree of order. Skin moisture increases after the use of the creams.
角质层是皮肤的最外层，因此它是身体和环境之间的决定性屏障。角质细胞和板层脂质层的组合防止身体水分流失，并防止外来物质渗透。ATR-FTIR（衰减全反射傅里叶变换红外）光谱法已被证明是一种用于选择性研究最外层角质层的方法。它提供了关于皮脂含量、脂肪物质类型、角质层中水分含量和板层脂质膜有序度的信息。不同类型的皮肤（干性、正常和油性）主要在皮脂含量上有所不同，但在脂肪组成和脂质有序度上也有所不同。与模型脂质混合物的比较表明，在生理条件下，角质层脂质主要以固定的凝胶形式存在。在清洁过程中，皮肤会去除大部分皮脂。皮肤会通过迅速分泌皮脂来应对脱脂过程。使用温和的面部清洁乳液清洁后，重新达到相同的脂肪状态所需的时间比使用表面活性剂沐浴露更长。皮肤霜会改变皮肤的水分和角质层脂质的有序度。具有与角质层脂质相似结构的层状霜会增加皮肤脂质膜中烷基链的有序度（仿生原理），而常规的油包水霜则会降低这种有序度。使用面霜后，皮肤水分会增加。
