Understanding the Epidermal Barrier in Healthy and Compromised Skin: Clinically Relevant Information for the Dermatology Practitioner
The role of the stratum corneum (SC) and several associated epidermal barrier (EB) functions in both healthy and compromised skin have gained increased recognition over more recent years...It is important to recognize that the EB represents a collection of specific diverse functions, many of which occur primarily within the SC. These include maintenance of water content and balance (permeability barrier), prevention and responses to invasion by microbial organisms and antigens (antimicrobial barrier and immune response barrier), reduction of the effects of ultraviolet (UV) light exposure (photoprotection barrier), and mitigation of the effects of oxidative stresses (antioxidant barrier).
Exogenous factors that can alter the integrity of the SC cause an increase in transepidermal water loss (TEWL) and alterations of SC proteins and lipids, progressively leading to compromised skin. Unless these factors are adequately countered by SC self-repair mechanisms and/or moisturization, the SC becomes overstressed, with continued increased TEWL leading to incomplete desquamation, loss of skin elasticity, increased skin rigidity, and epidermal proliferation...
In some individuals, underlying skin status and disease states, such as atopic dermatitis, innate xerosis, ichthyosis, psoriasis, diabetes, and increased age, exhibit inherent SC impairments, which predispose to increased TEWL, and when adversely affected by the aforementioned exogenous factors, the magnitude of EB permeability barrier compromise is further compounded.
There is a body of evidence to show that optimal management of many skin diseases, including eczematous dermatitis, acne vulgaris, rosacea, psoriasis, and xerosis, includes appropriate skin care. Incorporation of a gentle (nonirritating) skin cleanser and a well-designed moisturizer/barrier repair formulation can contribute to improvement of disease-associated signs and symptoms and can mitigate cutaneous irritation caused by certain topical medications. The distinction between moisturizers and topical barrier repair products is not clearly defined. Conventional moisturizers, available over-the-counter (OTC), can be purely occlusive (i.e., petrolatum, lanolin), or can contain both occlusive agents (i.e., petrolatum, occlusive/protective emollients) and humectant ingredients (i.e., glycerin, hyaluronic acid), designed primarily to reduce TEWL and increase SC hydration...there are also OTC moisturizer formulations that contain physiologic lipids (i.e., ceramides, ceramide precursors, fatty acids) and other special additives (i.e., niacinamide) that can assist in barrier repair.