Controlling the microclimate of the skin though the application of occluding films

The skin barrier is a responding membrane that separates environments with profoundly different
water contents. This implies a substantial water gradient across the skin membrane, which controls
transepidermal water loss (TEWL) and skin hydration. We define the microclimate of the skin as
the activity of water in the outermost layer of skin. By applying an occluding film composed of a
pharmaceutical or cosmetic formulation on the skin surface, it is possible to alter the resistance to
water evaporation from the body and to increase the microclimate at the skin surface. This way, the
occluding film can be used to increase the skin hydration.
In this study, we develop a quantitative method to predict how occluding creams affect skin
hydration. The cosmetic or pharmaceutical product forms a film at the skin surface, which is
described in terms of its specific occlusivity. We present a theoretical model that couples transport
and hydration in responding skin membranes after the application of the film, and an experimental
method to determine the specific occlusivity of films. Finally, we combine the experimental
measures with the theoretical model to obtain a quantitative tool to predict how occluding creams
affect the skin microclimate, the TEWL and the hydration of the upper layer of stratum corneum.