Cosmeceuticals: Function and the Skin Barrier

Published on 15/03/2015 by admin

Filed under Dermatology

Last modified 15/03/2015

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Chapter 2 Cosmeceuticals: Function and the Skin Barrier

THE STRATUM CORNEUM BARRIER AND THE ENVIRONMENT

Although the stratum corneum is an excellent and resilient barrier, the superficial layers are readily disturbed by low humidity, wind, sun, detergents, solvents, and other chemicals. The result is dry skin. What we experience as dry skin is not simply skin that lacks water but dysfunctional skin where aberrant desquamation leads to an accumulation of corneocytes at the skin surface (Fig. 2.3). The skin feels rough; looks dull because light is scattered by the uneven surface; looks pale because the pinky glow from the microcirculation is obscured; may show visible scaling, and is susceptible to irritation. All this is a consequence of dehydration at the skin surface.

Water is also important for maintaining the elasticity of the stratum corneum. Without water the skin feels tight and may crack in regions subject to stretching forces (e.g. knuckles). Ultraviolet (UV) radiation, which we mostly associate with sunburn in the short term and photoaging over time, may also damage the stratum corneum by disrupting the conversion of filaggrin to NMF (natural moisturizing factor).