Moisture retention in a (in vitro) porcine skin substrate

Model porcine skin samples were evaluated for moisture retention when subjected to various cosmetic treatments. Moisture retention was evaluated by two methods - via the Nova Dermal Phase Meter (DPM), and via weight loss measurements during moisture evaporation. In both measurements, skin samples were placed in dry-air environments. Although it is rare that skin in vivo would be subjected to such dry conditions, the evaluation proved useful in differentiating: (1) factors affecting the two types of measurements, and (2) the types of treatments. In initial experiments of the DPM method, it was found that the DPM level, usually attributed to the moisture level of the skin, was highly susceptible to the ionic strength of the skin treatment. Skin samples treated with solutions having higher salt concentrations exhibited higher DPM levels. It was also found that the duration of the DPM signal, during evaporative moisture loss from the skin sample, was relatively constant with changes in ionic strength. The duration could thus be used as a gauge of how well the skin retained moisture in the dry environment. A number of measurements of DPM duration were performed for skin samples treated with simple mixtures and more complex formulated products. The durations were correlated with water loss rates determined from gravimetric experiments.