Stratum corneum fatty acids: their critical role in preserving barrier integrity during cleansing

Stratum corneum (SC) bilayer lipids, specifically fatty acids, ceramides and cholesterol, contribute to the permeability barrier function of the skin. Normal skin cleansing is associated with damage to the SC lipids because cleanser surfactants, in addition to providing the desired effect of solubilizing and facilitating the removal of sebum and skin soils, have a propensity to disrupt bilayer lipids by extracting endogenous skin lipids or intercalating into the bilayer. Disrupted SC lipids are associated with a variety of pathological skin conditions, as well as with dry skin induced by harsh cleansing. In an attempt to preserve the barrier and mitigate the damage caused by frequent normal cleansing, the incorporation of physiologically relevant lipids into skin cleansers has become common in leading cleansing products. It has been noted that fatty acids are more susceptible to surfactant-induced removal than other lipids (eg, ceramides), an observation that may form the basis for a critically important strategy for replenishing SC lipids. This review will focus on the role of fatty acids in the structure and function of the SC, and the rationale for incorporation of stearic acid into moisturizing body cleansers to minimize their extraction by surfactants and replenish lost fatty acids to promote skin barrier preservation.