Skin hydration is at its lowest now due to fluctuating temperatures and humidity levels, resulting in dry, scaly skin. Other factors contribute to dry skin as well: harsh soaps, hot water, medications such as diuretics and retinoids, and diseases such as diabetes and hypothyroidism all contribute to dry skin. Dry skin is unsightly, uncomfortable, and can exacerbate existing skin conditions such as eczema and psoriasis.
The care of dry skin is a surprisingly complicated subject due to the variety of treatments available. All skincare treatments work at some level work to moisturize, exfoliate, or moisturize and exfoliate the skin. In order to understand the best treatment options available, the topics of both moisturization and exfoliation will be examined in regards to dry skin. However, since the biological process affected by both treatments is the same, a brief description of skin function, structure and maintenance is presented first.
The skin is the largest organ of the body, whose chief function is to act as a defensive barrier for the body's underlying tissues and organs. When intact, the skin protects the body from adverse events, such as dehydration and bacterial invasion. The impermeable nature of the skin is due to the uppermost layer of the epidermis, the stratum corneum. This skin layer is composed of highly differentiated, flattened, non-viable cells rich in keratin known as corneocytes. When the stratum corneum is classically likened to a brick wall, the corneocytes are the "bricks", held together by the "mortar", proteins known as corneodesmosomes.
Maintenance of the skin barrier depends on continual epidermal cell differentiation and stratum corneum replacement. In order to allow for continual cell turnover, the stratum corneum is continually shed in a process known as desquamation. Desquamation occurs by enzymatic hydrolysis of the corneodesmosomes, resulting in loss of cohesion between the corneocytes. The liberated corneocytes are then gently sloughed off the surface of the stratum corneum unobtrusively. The process is so orderly, that dust, composed in part of shed skin cells, is usually the only evidence desquamation is occurring.
Normal enzymatic functioning depends on the levels of several components of the stratum corneum: water, lipids and natural humectants. Abberrant levels of these components lead to decreased enzymatic activity, resulting in incomplete degradation of the corneodesmosomes. The retention and buildup of the corneocytes and subsequent fracture of the clumps gives the appearance of flaky, scaly skin. Two approaches, separately, or in tandem, can address abnormal desquamation. First, moisturizing promotes normal enzymatic action by affecting the environment of the stratum corneum, and second, exfoliation, mechanical or chemical, removes built-up corneocytes.The next two parts of this series will separately address both approaches; Part II will address moisturization technologies; Part III exfoliation.
Nicole is a research scientist with over 20 years experience and is the co-author of several patents and peer reviewed journal articles. Having been a cosmetologist at one time, she is naturally interested in beauty products. Find her on her blog "A Chemist's View of Beauty" where she discusses how and why beauty products work. From there, buy Nicole's favorite skincare products or use your new knowledge to find the best products for you. Nicole also welcomes comments and suggestions for future articles.
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Skin Structure and Function
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