Repair Kinetics of the Stratum corneum under Repeated Insults

Background: The stratum corneum (SC) structure and functions are altered by surfactants. Enhancing the repair mechanisms is a goal for some skin care formulations. Aim: To design an experimental procedure allowing the discrimination of repair efficacy for topical products applied to threatened SC. Method: Controlled SC strippings followed by repeated forearm soak sessions in surfactant solutions were used to compromise the SC barrier function in 20 volunteers. Two test formulations were compared. They were applied twice daily for 2 weeks before initiating the SC damages, and for the next 2 weeks while sustaining the procedure of soak sessions. Daily assessments involved objective measurements of parameters including transepidermal water loss, the value of the passive sustainable SC hydration and the epidermal turnover rate using the dihydroxyacetone test. Result: The experimental procedure allowed to clearly distinguish the differences in the kinetics of SC repair between the topical formulations. In the present study design, the repair of the barrier function mirrored the SC renewal. Conclusion: The present experimental design slows down the repair rate of the SC barrier function. Thus, it increases the sensitivity of biometrological measurements assessing some of the major SC properties. It also better mimics the common in vivo situation experienced by subjects chronically exposed to irritant xenobiotics.