A method to evaluate skin moisturizers in vivo

Abstract

Blank demonstrated that water is the only plasticizer of human stratum corneum. Moisturizers attempt to add and hold water within the horny layer, and have previously been evaluated subjectively or in vitro. By passing a stream of dry nitrogen over skin, then through an electrolytic moisture analyzer, moisture present at the skin surface will be detected. This technique has been utilized to measure transepidermal water loss and the inhibition of water loss from skin by various investigators. However, when this same procedure is done on normal human skin, higher values indicate the presence of more moisture. The more moisture detectable at the surface, the more moisture available for keratin to absorb. By applying the moisturizers to plastic film and the skin, it can be demonstrated that water is not detectable after a few minutes on the plastic, but is detectable on skin at higher than control (transepidermal water loss) values for several hours. The technique can demonstrate enhanced moisturization from plastic occlusion and wet dressings as well as the drying effect of benzoyl peroxide gels. It allows objective rank ordering of moisturizers by monitoring moisture enhancement rather than occlusivity of applied substances.