Any detailed research you may have done about the skin would have returned you with the term ‘skin barrier’, or in scientific terms the ‘stratum corneum barrier’. You may be aware of how important the skin barrier’s function can affect the condition of the skin, but how exactly does the skin barrier work?
Skin hydration and the stratum corneum barrier has been active areas of study for many years. Yet, consumers are only beginning to get their interest piqued about the skin barrier, largely due to many marketing techniques. Before you commit to any product or treatment that promises to ‘repair’ the skin barrier, have a read on what these terms and processes mean.
The stratum corneum barrier
The skin barrier prevents foreign material from entering the human body. But it does more than just that. It also prevents water loss and serves as a shield against environmental factors. The barrier works to maintain the body’s homeostasis (or stable equilibrium) level. The loss of water from the body through evaporation from the surface of the skin is common, thus a need to keep our corneocytes hydrated.
Corneocytes are the cells found in the stratum cornum layer, that is the outermost layer of the epidermis. These cells are formed through cornification, where the skin cells develop tough protective layers or structures, creating a physical barrier for the skin. When deprived of water, dry skin may be more prone to crack open at stress.
The environment’s humidity also affects the corneocytes. As the level of humidity can vary, corneocytes get their source of hydration from the body, in order to maintain equilibrium with the environment. This may explain why our skin feels drier in winter. The skin battles harsh winds, depleting the skin’s moisture layers.
Skin hydration is an important factor when considering how to attain healthy skin. We look at the stratum corneum’s water content when analyzing skin hydration, with healthy skin containing more than 10 per cent water.
A mixture of water-soluble compounds called natural moisturizing factor (NMF) have been found to affect water content levels. The arrangement of lipids (fats) in the stratum corneum is also important, as it serves as an effective barrier to the passage of water through the layer. A poor arrangement can lead to transepidermal water loss (TEWL). TEWL is essentially when water diffuses and evaporates from the skin surface. Even though this is a natural process, excess TEWL is undesirable as it can lead to many unwanted skin conditions.
TEWL and Moisturizers
TEWL has been one of the most commonly used methods in the skin care industry to measure skin hydration as it directly correlates with skin barrier dysfunction. Healthy skin would score a low TEWL value as it would mean less water loss.
In the same vein, most moisturizers are put to the test by using TEWL values. A good moisturizer should help decrease TEWL. Moisturizers have remained as a ‘staple’ in basic skincare. Yet, not many may fully understand its function, thus some are unable to choose a suitable moisturizer for their skin needs. An effective moisturizer should protect the skin by stimulating and augmenting its natural barrier function, whilst catering to the skin’s requirement for moisture. Environmental attacks on the skin are also shielded with a proper moisturizer which can slow down skin ageing.
What happens if the water content of the stratum cornum falls below a desirable level? Normal desquamation is not able to take place, that is the shedding of the outermost skin layer. With insufficient hydration, skin cells will adhere to one another and accumulate on the surface layer. Visible changes associated with this phenomenon include dryness, roughness, scaling and flaking.
Certain cosmetic ingredients have become a cult favourite in recent years by targeting the stratum cornum water content, such as glycerol (also known as glycerin) and hyaluronic acid.
This ingredient exists in the stratum cornum as a natural endogenous humectant. It has shown that changes in the stratum cornum’s water content correlate with the glycerol content in the layer. Such results have driven the development of glycerol-containing moisturizers. Check the ingredient list of your moisturizer, this star ingredient should appear in any effective moisturizer.
Though it is known as a major component of the dermis (deeper layer of the skin), hyaluronic acid is also found present in the outermost layer. It plays an important role in regulating the skin barrier function and hydration. Although the skin care industry may recognize hyaluronic acid as a powerful humectant (attracts water to hydrate the skin), this molecule also participates in cellular functions. Hyaluronic acid influences cell-cell interactions that lead to normal structure of the skin barrier.
Though the mechanisms for skin hydration remain complex, a simple understanding about the skin structure and function is crucial when looking for an appropriate product or treatment. With these complex terms tackled, you are now one step closer to understanding your skin and its needs. If your current skincare routine does not yield desired results, you can consider cosmeceuticals as the alternative. A combination of ‘cosmetics’ and ‘pharmaceuticals’, cosmeceuticals are products with bioactive ingredients that can bring pharmaceutical effects to the skin barrier and health.
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Tags: cosmeceuticals, glycerol, hyaluronic acid, hydration, Moisturizer, skin ageing, skin barrier, TEWL