A dynamic random-effects model for recovery of skin barrier function: evaluation of the efficacy of different skin care products

Apparently, the use of mathematical and statistical models to describe the structure and function of the skin barrier is rather limited. The skin barrier protects the body against uncontrolled loss of water and desiccation, and prevents environmental substances from entering the skin. A simple measure of the barrier function is the transepidermal water loss (TEWL), which is easy to measure. Healthy skin has low TEWL values, whereas various skin diseases result in high TEWL values and eventually in the development of dry skin. The use of skin care products can protect and prevent dry skin. In this study several different trial formulations are compared with respect to their abilities as skin care products. The study is performed as a longitudinal study on mice, where the skin barrier is broken by means of acetone and then treated with one of the formulations. We analysed the data by means of a semimechanistic random-effects model with similarities to pharmacokinetic models. In the model each formulation is characterized by two parameters: one that corresponds to the initial barrier restoration effect and one that corresponds to the elimination rate.