Properties of Emulsions: Structure and Skin Penetration

Today's cosmetic emulsions are not simply mixtures of oil, water and emulsifier; they also contain a number of active ingredients functioning to ameliorate the condition of the skin, such as skin hydration or the barrier properties of the stractum corneum (SC). Most of these ingredients will work only if they penetrate the SC or the deeper layers of the epidermis. The extent and rate of penetration depend not only on the diffusion and solubility properties of the ingredietn molecule itself, but also on the effect of the cosmetic vehicle of the diffusion process.