Background In vivo confocal Raman spectroscopy (CRS) revealed a clear correlation of age and dermal water content, indicating increasing water content of the dermis with increasing age. This enhancement of water has been interpreted as an age‐dependent depletion, of proteins, mainly of collagen. Chronical sun exposure is known to destroy the collagen network of the skin, which leads to the signs of photoaging as the formation of wrinkles. Noninvasive in vivo measuring techniques for photoaging are limited. Therefore, sensitive techniques to quantify even mild degrees of photoaging in a clinical setting are of high interest. We used CRS to measure the water content in human dermis in vivo, assuming that additionally to the increase of water content in intrinsic aging, photoaging would lead to further collagen depletion and an additional increase in water content of the dermis. Materials and Methods A panel of 24 female subjects of different age‐groups and scores of photoaging was recruited. A ranking of high resolution dorsal forearm photographs was used to classify the degree of photoaging with high precision. After that, CRS water content and collagen measurements were performed in the photoexposed dorsal as well as the photoprotected volar dermis of the subjects. Results A positive correlation of water content in the dermis with age could be confirmed (r = .550). Further, a positive correlation between water content of dorsal dermis and photoaging ranks was observed (Pearson's r = .417). Conclusion Assessment of water content in the dermis with confocal Raman spectroscopy was found to be a promising method to measure the degree of photoaging in human subjects in vivo.

Objective: Tape stripping is an often-used non-invasive destructive method to investigate the skin penetration of a substance. In recent years, however, the suitability of confocal Raman spectroscopy (CRS) as a non-invasive method of nondestructive examination of the skin has become increasingly apparent. In this study, we compared invasion and depletion penetration and permeation kinetics of a 2% caffeine solution with and without 1,2-pentanediol as a penetration enhancer measured with CRS and tape stripping.Methods: Porcine skin was used for tape stripping and human skin for CRS. 2% caffeine solution was applied to the skin for different incubation times. Human skin was then examined by CRS while caffeine was extracted from porcine skin and quantified via reverse-phase HPLC. Fluxes were also measured and calculated by sum of the total amounts of caffeine penetrated into the skin.Results: Without penetration enhancers, there is hardly any difference between the penetration profiles of the two measurement methods for invasion, but the curves for depletion are different. Furthermore, the calculated flux values for the invasion are almost identical, but for the depletion the tape stripping values are about twice as high as the CRS values. Conclusion:The relevance of conducting invasion and depletion studies became clear and was able to show the still existing problems in the comparability of CRS and tape stripping.

Background:The purpose of this pilot study was to provide information about the washout-dependent depletion of important skin components in the horny layer of the scalp. They were taken as markers for scalp drying effects of cosmetic cleansing products and were measured directly in vivo. Method:In vivo confocal Raman spectroscopy was used to measure the depletion of the total natural moisturizing factor (total NMF) and some of its components (urea and lactic acid) as well as a fraction of stratum corneum lipids, after repeated washing with a standard shampoo on the human scalp. Results:The measurements showed a reduction in the amount of NMF and lipids of the stratum corneum caused by repeated shampooing. Conclusion:Confocal Raman spectroscopy is an innovative technology that can be used successfully in vivo on the hairy scalp. The loss of the most important skin components caused by hair washing can be quantified directly with this technology. The method is valuable to support the development cosmetic cleansing products, as it is suitable to directly compare the effects of different product candidates on the human scalp in a most realistic way.