GUOJIN LU¹*, DAVID J. MOORE²
*Corresponding author
1. Global R&D, Ashland Inc., 1361 Alps Road, Wayne, NJ 07470, USA
2. TRI Princeton, 601 Prospect Avenue, Princeton, NJ 08542, USA

Abstract

Surfactant-based cleansing products can cause skin damage and/or irritation due to surfactant-skin interactions, which can compromise skin barrier function. Such interactions need to be minimized. In this work, skin impedance measurements were conducted in vitro on porcine skin using vertical Franz diffusion cells to investigate the impact of surfactants, as well as skin cleansing formulations, on skin barrier integrity and function. This method can guide the development of milder cleansing formulations resulting in less or no skin damage/irritation. Examples of some beneficial formulation additives are illustrated and discussed. The study demonstrates that skin impedance is a useful proxy for skin barrier function and can be utilized as a routine approach to screen surfactant containing formulations for their propensity to compromise the skin barrier.

INTRODUCTION
Stratum corneum (SC), the outmost layer of the skin, plays a critical physiological role in protecting the body from stresses in the external environment (1). However, cleansing the skin with soap bars and other surfactant-based cleansing products can reduce skin barrier function, as frequent exposure to surfactants leads to various degrees of skin damage and irritation, including dry and itchy skin. It is widely established that the cleansing process also causes damage to the skin by denaturing proteins and/or solubilizing or disrupting the organization of stratum corneum (SC) lipids (2-3). As the result, skin is often left dry and flaky after frequent cleansing as surfactants interact with the skin and weaken its natural defensive SC barrier function. The undesirable effects of surfactants on skin also include poor skin appearance and increased skin tightness. These effects are greater when the ambient temperature and humidity levels are relatively low. An additional negative effect of cleansing is that surfactant molecules may penetrate into the SC and induce further skin irritation; such effects are greater for individuals with sensitive ...