The importance of this chapter is considered taking into account the following facts: the new European legislation is much more concerned with the protection of the consumer from misleading claims related to efcacy [1]. One observes a tightening up of the substantiation of claims: there must be relevant data of substantiation on a le to back up any claims, and there is a proposal for establishing common criteria for all types of claims. In order to help and sustain the cosmetic industry, the “Cosmetics Europe Personal Care” Association (previously COLIPA) representing the positions of the European cosmetic industry has published two guidelines.