On the use of infrared spectroscopy for the in vivo measurement of the water content of the horny layer after application of dermatologic ointments.

Infrared-spectroscopic investigations of the water content of the stratum corneum after application of emulsions and wash solutions are reported. As a methodologic variation infrared spectroscopy is applied after stripping the skin to determine the hydration of various depths of the stratum corneum by ointments. Using soap as an example, a method of correcting the overlap effects between the ointment and skin spectrums is presented which expands the application possibilities of infrared spectroscopy. An o/w emulsion with plenty of water and a w/o emulsion containing less water produce to almost the same degree a hydration of the deeper layers of the stratum corneum which lasts for at least 40 min. The report in the literature that soap solutions produced a stronger hydration of the stratum corneum and surfactant solutions is not supported.