In vivo Raman Confocal Spectroscopy in the Investigation of the Skin Barrier.

The epidermal barrier, predominantly attributed to the stratum corneum (SC), is the outermost part of our body that comprises multiple defensive functions against exogenous attacks and the loss of body substances, e.g. water. A novel investigative method, in vivo Raman confocal spectroscopy (RCS), is employed to study the composition of the epidermal barrier and compounds penetrating the epidermis both in a space-resolved manner. By using this method, a semiquantitative analysis of skin barrier constituents can be evaluated, namely SC lipids, natural moisturizing factor components and sweat constituents. The technique enables to examine epidermal barrier impairment in experimental settings as well as the penetration of exogenous substances into the epidermis, e.g. retinol. RCS can reveal microcompositional changes in the skin barrier as a function of age. We also review the use of RCS in studying antioxidant defense components. This chapter discusses the application of in vivo RCS in the investigation of the epidermal barrier.