Physico-chemical in vitro methods for determination of the skin compatibility of surfactants.

Abstract

In order to reduce the number of animal tests there have been some efforts to establish in vitro methods for testing cosmetic products, especially for the skin compatibility of surfactants.The main principles of the published physico-chemical methods for in vitro testing of surfactants are summarized. They are mostly based on the interaction of surfactants with proteins and protein structures, e.g. isolated skin layers. Water binding capacity, adsorption, denaturation, solubilisation benetration and other properties have been investigated.The practical application of these methods implies thorough knowledge of their possibilities and limits. Thus the swelling behaviour of isolated pig epidermis has been studied in detail to develop an in vitro test for the skin compatibility of surfactants. The water uptake of epidermis strips in surfactant solutions was gravimetrically measured. Dependent on the surfactant structure the swelling values were different and characteristic. The effects of various types of surfactants and their mixtures are discussed and compared with skin irritation values of human and animal tests. Anionic surfactants displayed a satisfactory ranking correlation of swelling and irritation values.