The Skin Barrier

The largest organ of the human body is the skin with its ~2 m² surface area that envelopes the whole organism defining its physical border and which most importantly provides a barrier against internal organ dehydration and external penetration of noxious substances.

The critical importance of the skin barrier is appreciated when it is lost such as in skin burns or compromised such as in atopic dermatitis, affecting the overall wellbeing of the individual. Moreover, it has been shown that the skin barrier function undergoes a maturation process during the first years of life. It is therefore of interest to identify skin care routines such as washing and bathing that would not be damaging to the skin barrier and if possible enhancing its protection.

Furthermore, barrier enhancement aids in the prevention and treatment of certain conditions such as atopic dermatitis. Recent scientific discoveries in skin biology and formulation science have advanced the understanding of the regulatory mechanisms that control skin barrier homeostasis as well as our knowledge of skin-product interactions. Application of this knowledge has led to the design of appropriate skin care products and the design of tests that can demonstrate barrier-related benefits.

The skin is a barrier that protects the body from the outside world. Defense functions are localised in the stratum corneum (SC), which typically includes about 9–15 corneocyte cell layers (Corneocyte cells form layers within the skin's SC, the outermost layer of the epidermis. These layers are divided into two main parts: the deeper, more compacted stratum compactum and the uppermost, looser stratum disjunctum) that consist of packing of keratin filaments and filaggrin of corneodesmosomes (main intercellular adhesive structures in the skin's stratum corneum, holding dead skin cells (corneocytes) together to form a protective barrier) Elias depicted the SC as a brick wall, with the corneocytes similar to bricks and lipid lamellae acting as mortar. These lipids are composed of approximately 50% ceramide, 25% cholesterol, and some long-chain free fatty acid. Lipid lamellae play a crucial role in the barrier function.

Recent advances in the understanding of pathophysiology of the epidermal barrier and its critical role in the pathogenesis of AD led to increased interest in barrier repair therapies. But what does “barrier repair therapy” mean? Ideally, the emollients should normalize the epidermal barrier function by reducing transepidermal water loss (TEWL) and improving SC hydration.

Studies on barrier repair treatment, either in animal models or in humans, showed that adequate lipid replacement therapy reduces the inflammation and restores epidermal function comparable to topical fluticasone cream.

Urea, a well-known humectant used in various topical emollients, has been very recently shown to normalise barrier function. There are several nonprescription products that proclaim barrier repair properties. Chinese herbal mixtures (CHM) had been often claimed beneficial in treatment. A recent study had demonstrated that topical CHM accelerated barrier recovery following acute barrier disruption by increased epidermal lipid content and mRNA expression of fatty acid and ceramide synthetic enzymes, mRNA levels for the epidermal glucosylceramide transport protein, and mRNA expression of antimicrobial peptides.

Skin care products that contain high lipid substances are frequently applied for the care of dry skin and inflammatory skin conditions. Oils, both pure and integrated, are commonly applied for skin care. The oils assist the native lipids of the SC to provide a better barrier function and consequently help moisturising the skin. The decreased TEWL values specify that the use of the oils leads to a semi-occlusion of the skin surface. Similar results were attained for both mineral and vegetable oils. Paraffin, jojoba, and almond oils were shown to penetrate equally into layers of SC, while coconut oil, used as a moisturiser, was found to be as effective and safe as paraffin oil.

Proksch et al. found that bathing in magnesium-rich (5%) Dead Sea salt solution improves skin barrier function, augments skin hydration, and decreases inflammation in atopic dry skin. A recent study revealed that treatment of atopic dermatitis by a Dead Sea mineral enriched body cream, improves physiologic and clinical severity scores of the disease, and may serve as a maintenance therapy for AD patients.

Understanding of various approaches for restoration of skin barrier, especially the role of topically applied mixtures of cholesterol, ceramides, and essential/nonessential free fatty acids (FFAs) allows for the strengthening of the compromised skin barrier and alleviation of symptoms and discomfort associated with skin barrier disorders. Ceramide containing products on the market are commonly available and offer protection and reparative benefits to the skin barrier.

The above is NOT MY OWN WORK and taken from:

Valdman-Grinshpoun, Y., Ben-Amitai, D., Zvulunov, A., Barrier-Restoring Therapies in Atopic Dermatitis: Current Approaches and Future Perspectives, Dermatology Research and Practice, 2012, 923134, 6 pages, 2012. https://doi.org/10.1155/2012/923134

Also:

Stamatas, Georgios N., Zvulunov, Alex, Horowitz, Paul, Grove, Gary L., Skin Barrier Protection, Dermatology Research and Practice, 2012, 691954, 2 pages, 2012. https://doi.org/10.1155/2012/691954

All the above is from open access articles, available for use under the CC BY 3.0 license (creativecommons.org/licenses/by/3.0/) . I have modified the original text (which essentially refers to Atopic Dermatitis though is still relevant)