One of the most expensive stages in cosmetic product formulation is in vivo efficiency evaluation. In the depilation field, work of adhesion (Wa) estimation using wettability measurements for depilatory wax and leg hair, an in vitro method, has allowed a first formulated product screening, and then the selected formulation showing the best Wa has been tested in vivo. Leg hair constitutes a difficult support to study because of its short length and difficulty in selecting samples. The aim and the originality of the work described in this paper is to show, from a morphological and a physicochemical study, that scalp hair roots can be used as a global leg hair model for the estimation of the formulated depilatory wax adhesion. Formulated depilatory wax comparison from Wa measurements using scalp hair roots and in vivo tests are correlated, thus validating our global leg hair model.
© 2003 Society of Chemical Industry