ABSTRACT
In the last 10 years, confocal Raman microspectroscopy (CRS) has emerged as a tool for the in vivo, noninvasive, and direct measurement of the molecular composition of the skin and, in particular, of the stratum corneum (SC). This chapter describes the most frequently used technical implementations based on the principle of CRS for in vivo skin analysis. CRS can be used to investigate the transcutaneous penetration of topically applied substances, provided that these have a distinct Raman signature and are applied in sufficient amounts to be detected by currently available spectrophotometers. A causal pathway between the impairment of the skin barrier function, causing higher transcutaneous penetration of water-soluble chemicals, and skin hyperreactivity has been hypothesized. Natural moisturizing factor (NMF) is an efficient humectant, helping to bind water within the cells and to maintain skin hydration and flexibility. An imbalance of the intercellular lipids has been suggested among the mechanisms leading to an impaired barrier function in sensitive skin.
