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Impaired barrier function leads to transepidermal water loss (TEWL), resulting in dry, flaky skin.
When you think of or look at skin, what is the first thing that comes to mind? Does it have a healthy glow? Is it a certain color? Is it wrinkled or blotchy or just plain dull? Skin is the first thing you notice when you look at yourself and others, and it is also your body’s first line of defense from UV exposure, weather, germs and other insults.
As skin care professionals, you look at skin more closely and, more importantly, you try to understand why skin looks a certain way. The skin is the body’s largest organ, and is part of both the integumentary system and the excretory system, where it is responsible for removing waste from the body in the form of perspiration, or sweat. Skin is a canvas, painted by each individual’s genetics, lifestyle choices and product use, requiring skin care professionals to understand skin function and ingredient mechanism of action in order to provide each client with the best treatment plan for their skin, regardless of Fitzpatrick type or condition.
The skin is comprised of two main sections, separated by the stratum basale, or basal layer. The dermis, which is the lower portion of the skin, lies just above the adipose layer; the epidermis, the outermost layer, is protected by the stratum corneum (SC). Each section of the skin works together and, if just one component is not functioning properly, then the entire structure can become compromised. In short, outer, visible skin is a reflection of everything that is happening underneath.
The dermis is made up of three major types of cells: fibroblasts, macrophages and adipocytes. It is also composed of what is known as the extracellular matrix (ECM), which contains collagen for strength; elastin for elasticity; and glycosaminoglycans (GAG) that support and maintain collagen, elastin and turgidity within the spaces between the cells. GAG also encourage the ability of these matrix fibers to hold on to moisture, keeping them soluble. Because the ECM is the support system for the epidermis, it is crucial to keep it healthy and functioning properly. If this structure becomes weakened and unable to provide the necessary support required to maintain the epidermis, then outward signs of aging begin to appear, such as wrinkles, sagging, enlarged pores, loss of elasticity and, ultimately, a loss of the youthful appearance associated with firm and healthy skin.
The epidermis provides the human body with a barrier from external insults and is reliant upon the dermis for support and hydration. The SC, the outermost layer of the epidermis, is comprised of lipids, such as ceramides, cholesterol and free fatty acids that maintain hydration and protect the new cells rising from the basal layer. As mentioned previously, the ECM within the dermis is the scaffolding, or the support structure, that gives the epidermis its bounce and elasticity. When explaining this to clients, a good comparison is to a mattress and box springs. If the box springs (ECM) weaken, then the mattress (epidermis) sags. Another important function of the dermis is to provide the epidermis with hydration. Because limited amounts of water are able to penetrate through the epidermis from the outside, it must be able to attract and hold the moisture that is provided by the dermis from the inside. Because people lose several ounces of water through the epidermis on a daily basis, known as transepidermal water loss (TEWL), a delicate balance must be maintained between the dermis and the epidermis. Should TEWL become excessive, the result is impaired barrier function, meaning the epidermis is no longer providing the barrier protection that is vital to overall skin health. Impaired barrier function presents as irritated, inflamed and flaky skin, often giving a rough, red and dry appearance. Imagine the outward appearance of skin with an impaired barrier and without ECM support, and you can see the importance of these two major components and how they directly affect skin health.