Forster, Th., W. Pittermann, M. Schmitt, and M. Kietzmann. Skin Penetration Properties of Cosmetic Formulations. Skin Penetration Properties of Cosmetic Formulations. Perspectives in Percutaneous Penetration - 6^th International Conference. (Leiden, Sept. 22-26, 1998).

Today's cosmetic formulations are not only simple mixtures of oil, water and emulsifiers but also contain a lot of active ingredients. The ingredients only work if they are able to leave the cosmetic emulsion penetrating the surface or reach the living part of the skin. As examples for the penetration studies the bioactive ingredients such as oil and water soluble vitamins were chosen. The penetration properties in horny layers and skin were evaluated under leave-on and rinse-off conditions for cream and shower gel formulations. Since simple penetration models can not match these various conditions a reliable experimental substitute for in-vivo tests on humans was used [bovine udder skin model - BUS].