Equivalence of face and volar forearm for the testing of moisturizing and firming effect of cosmetics in hydration and biomechanical studies.

The objective of the study was to compare measurements of skin hydration and of biomechanical properties performed on different zones of face and volar forearm. Two short-term (1 h) and two long-term (3 weeks) studies were conducted with a moisturizing and a firming product, respectively, on groups of female volunteers with dry skin. Measurements (Corneometer) and Dermal Torque Meter or DTM were performed on different zones of the face and of the volar forearm, 1 h after product application, and after 1, 2 and 3 weeks of repeated twice daily application. While the sebaceous-gland rich T-zone behaves differently, probably due to sebum/skin, sebum/product and/or sebum/measuring device interactions, there are no statistically significant differences between measurements made on temple, cheek, maxilla and volar forearm. The volar forearm is representative of the face for measuring skin hydration and biomechanical properties, and relevant for the assessment of the efficacy of cosmetic products destined for facial use.