What is the Skin Barrier?

The outermost layer of the skin is lined with dead skin cells called corneocytes and they are dead and flat cells without a nucleus, but they serve important roles in maintaining skin integrity by tightly holding our skin intact and protected from sensitizing agents in the environment, while preventing moisture loss to the surrounding in a process known as TEWL. 

Between cellular junctions is the intercellular lipid matrix - a mixture of ceramides, cholesterol and fatty acids that hold cells together. As keratinocytes mature and secrete natural moisturizing factors to keep skin hydrated and supple, the lipid matrix forms a waxy barrier that prevents water-loss, as the elevation of such is associated with many skin sensitivity issues such as eczema, atopic dermatitis, psoriasis…etc. 

Sounds like a perfect design, but in reality: 

• surrounding such as UV, humidity, dryness, pollutants, irritants
• skincare such as harsh chemicals and surfactants; or medications such as steroids
• excessive exposure to UV, exfoliants, and cleansing products
• heredity and(or) stress, often leading to conditions like eczema and psoriasis
• changes in skin acidity such as health conditions like diabetes (as high glucose levels affect inflammatory responses as well as lead to less acidic environment)

can all compromise the barrier function. 

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Major components of Skin Barrier

Cholesterol - helps to maintain the fluidity and the flexibility of the acid mantle preventing it from becoming too rigid or brittle. When the temperature is high, cholesterol’s presence makes the membrane more rigid. When the temperature is low, cholesterol inserts itself between phospholipids which tend to clump together to make our membranes more fluid, thereby maintaining its function through proper form.

Fatty Acids - contribute to the skin’s natural acidic pH and maintain microbiome health. The acidic environment helps to kill off harmful bacterial, so that’s why over-exfoliation or cleansing resulting in a disrupted barrier can actually aggravate acne. Omega-3s (alpha-linolenic acid) and 6s (linoleic acid) fatty acids also function as signalling molecules that regulate inflammatory responses, while linoleic acid triggers wound healing responses by increasing new blood vessel formation. 

Ceramides - their structures - hydrophilic head and hydrophobic tail - enable the tight binding of cellular junctions. They are also able to organize the membranes of our cells, decreasing their fluidity and stabilizing the membrane, resulting in an organized and coherent sealage that is highly waterproof within intracellular spaces of the stratum corneum.

While the body can make some of these components de novo, others are to be replenished through a healthy diet of vegetable oils, nuts, seeds, and eggs. For the specific purpose of maintaining a healthy skin barrier, these ingredients - especially ceramides - are also available in skincare formulas designed to protect the skin.