[Biophysical measurement of cutaneous hydration in vivo]

The skin, because of its involvement in health, comfort and aesthetics, is a particular "organ". Cutaneous hydration is essential for the dermatologist and the cosmetician. For the dermatologist, "dry skin" is a clinical sign of an often unclear pathogenetic disorder and for the cosmetician it is a discomfort related to aging, climatic effects or sun exposure and should be compensated or prevented. The essential measurement and objective quantification of cutaneous hydration has led to the development of various techniques, based on differing biophysical principles and studies aimed at providing better understanding of the mechanisms involved. Faced with an abundance of information and means, the aim of this review is to briefly present the various techniques and instrumental measurements of hydration in vivo, their biophysical principles and their pertinence for the clinician.