Lipids and barrier function of the skin.

The purpose of the present manuscript is to review the chemical and physical properties of epidermal lipids and to relate these properties to the formation and function of the permeability barrier of the skin. Lipids accumulate in small organelles known as lamellar granules as epidermal keratinocytes differentiate. This lipid is extruded into the intercellular spaces where it undergoes enzymatic processing to produce a lipid mixture consisting of ceramides, cholesterol and fatty acids. This intercellular lipid is uniquely organized into a multilamellar complex that fills most of the intercellular space of the stratum corneum. The barrier properties of the stratum corneum are related to the phase behavior of the intercellular lipids. It has been proposed that a structurally unusual acylglucosylceramide is thought to be involved in assembly of the lamellar granules, and a related acylceramide may have a major influence on the organization of the lamellae in the stratum corneum.