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Why They Are Important in Maintaining Healthy Skin
By Lisa Flynn
The skin is the largest organ of the human body with several important functions toperform. The skin protects us from the sometimes-harsh external environment (e.g.microbial invasion and physical injuries), regulates our body temperature, providessensory input and eliminates waste. The skin can lose its ability to perform thesefunctions when compromised or damaged.
While there are many causes leading to damaged or compromised skin, one mainpreventable cause is dry skin. The top layer of the skin, the epidermis, has an outer-mostlayer, the stratum corneum. The stratum corneum is where moisture content is controlled.Within the stratum corneum, two main components aid in this function--keratin andphospholipids. When the skin is healthy, these two components work in conjunction to keepout irritants and keep in moisture.
Dry skin occurs when the skin loses its phospholipid bilayers. The result is potentialirritants entering and moisture exiting through the skin.
Thus, moisturizers can be used preventatively or to help restore the stratum corneum toits more normal function.
There are two means in which to moisturize the skin. Moisture can be added back intothe skin or transepidermal water loss (TEWL) can be blocked or inhibited. TEWL is theprocess by which moisture migrates from the dermal tissues to the epidermis into thestratum corneum and evaporates into the atmosphere.
Moisturizers fall into two categories: lipids and humectants. Humectants attractmoisture, and depending on their size (molecular weight), they are either absorbed intothe skin or stay on the surface of the skin. Examples of humectants are glycerin, urea,and hyaluronic acid. Lipids perform differently than humectants by blocking moisture fromleaving the skin. They are occlusive or semi-occlusive materials that are appliedtopically, provide a barrier and allow skin to better restore itself. Common lipids arepetrolatum, lanolin, and mineral oil. Synthetic lipid materials are emerging technologies,which allow the lipid to penetrate the skin and fill spaces where natural phospholipidsare missing. Lipids work best when applied soon after soaking, bathing, or showering. Atthis time, your skin will retain some of the moisture, and a lipid-based moisturizer willprovide a barrier to moisture loss. The Skin Protectant Tentative Final Monograph for OTCdrugs lists multiple materials with specific active percentages that protect injured orexposed skin or mucous membrane surface from harmful or annoying stimuli. These productscan be used to lessen or inhibit TEWL. Some of the active ingredients are petrolatum, zincoxide, dimethicone, allantoin, and glycerin.
Our skin performs many important functions--moisturizing the skin is an important stepin maintaining healthy skin.
Lisa Flynn is a product director at Johnson & Johnson Medical Division ofEthicon, Inc. (Arlington, Tex).
Klein, L (1988) Maintenance of healthy skin. Journal of Enterostomal Therapy, 15(6), pp. 227-231.
Loden, M & Lindberg, M. Chapter 24 - Product Testing - Testing of Moisturizers, Bioengineering of the Skin: Water and the Stratum Corneum, pp. 275-289.
Skin Protectant Drug Products for Over-the-counter Human Use: Tentative Final Monograph, Federal Register, Vol. 48, No. 32, pp. 6820 - 6833.
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