Dry skin is a very common condition. Dry skin is one of the most common skin abnormalities. Although certain individuals are more susceptible to dry skin, the condition can affect anyone, regardless of age, gender, or skin type.
Dry skin occurs when the skin's outer layer (the stratum corneum) is depleted of water. The skin's outer layer consists of dead, flattened cells that gradually move toward the skin's surface and slough off. Called the stratum corneum, the outer layer has a critical protective role. When this layer is well-moistened, it minimizes water loss through the skin and helps keep out irritants, allergens, and germs. However, when the stratum corneum dries out, it loses its protective function. This allows greater water loss, leaving your skin vulnerable to environmental factors.
Under normal conditions, the stratum corneum has a water content of 10% to 30%. This water gives the skin its soft, smooth, and flexible texture. The water comes from the atmosphere, the underlying layers of skin, and sweat. Oil produced by skin glands and fatty substances produced by skin cells act as natural moisturizers, allowing the stratum corneum to seal in water.
We continuously lose water from the skin's surface by evaporation. Under normal conditions, the rate of loss is slow, and the water is adequately replaced. Characteristic signs and symptoms of dry skin occur when the water loss exceeds the water replacement, and the stratum corneum's water content falls below 10%.
Although most cases of dry skin respond well to self-care, some cases require professional medical care. Mild-to-moderate cases of dry skin usually respond well to self-care measures and over-the-counter products. However, professional medical care is needed for severe dry skin, dry skin accompanied by other symptoms, and dry skin that persists despite self-care measures. These patterns of dry skin may signal the presence of other skin conditions, other medical conditions, or drug side effects. Persistent dry skin can lead to complications such as inflamed skin (dermatitis) and infection. A primary care provider can treat some cases of dry skin, but more complex cases of dry skin usually require treatment by a dermatologist.
Any factor that damages the stratum corneum can interfere with its barrier function and lead to dry skin. These factors include long, hot showers and cold, dry air, detergents and solvents, or chafing and scrubbing. When the stratum corneum is damaged, water moves more freely towards the surface of your skin where it evaporates, causing your skin’s water content to fall.
Abnormal loss of skin surface cells may also play a role in dry skin. Normally, cells lost from the skin's surface are shed individually and unnoticeably. However, sometimes the cells stick together and resist shedding. As a result, the stratum corneum thickens. When the cells are lost, they are lost as large visible sheets called scales.
Some people inherit a tendency for dry skin. The moisture level of the skin is partly determined by genetics. Under identical conditions, different people will have normal, oily, or dry skin. Fair-skinned individuals seem to be more prone to dry skin than people with darker complexions.
The normal changes associated with aging often lead to dry skin. With increasing age, the skin's ability to produce sweat, oil, and other fatty substances diminishes. The skin cells also divide more slowly, and the skin thins and takes longer to repair. As a result, the water content of skin is reduced in older adults. This age-related dry skin is usually more pronounced in women than in men.
Dry skin is often caused or worsened by bathing and cleansing practices that strip natural oils from the skin. Our modern standards of cleanliness play a key role in the development of dry skin. Frequent, long, and hot showers and baths remove the skin's protective oils. Soaps (especially harsh soaps, deodorant soaps, and antibacterial soaps), detergents, and cleansers also remove the skin's oil. Skin-drying ingredients lurk in a variety of other personal care products, including antiperspirants and perfumes.
Dry skin is often caused by exposure to low-humidity environments. The cold, dry air of winter is one of the most common causes of dry skin. The amount of water in the stratum corneum varies with the humidity of the surrounding atmosphere. Low humidity levels have a drying effect on the stratum corneum. The humidity level is determined both by naturally occurring factors (the weather) and by manmade factors (indoor environmental controls.)
The cold, dry air of northern winters is one of the leading causes of dry skin. Central heating often compounds the problem by making indoor air just as dry as outdoor air. Dry skin that occurs in the winter months is often called winter itch.
The hot, dry air of desert climates can also cause dry skin. In addition, air conditioning used in many hot climates, both dry and humid, removes water from indoor air and has a drying effect on skin.
Dry skin can be a symptom of other skin conditions. Skin conditions often associated with dry skin include eczema, contact dermatitis, psoriasis, and ichthyosis (an inherited condition causing marked flaking of the skin).
Dry skin can be an important clue to the presence of underlying medical conditions. The appearance and texture of skin often provide important clues about your overall health. Dry skin can be a symptom of a wide variety of underlying medical conditions:
- kidney disease
- acquired immunodeficiency syndrome (AIDS)
- Hodgkins’ disease
- nutritional deficiencies
Dry skin can be a side effect of certain drugs. Dry skin is a possible side effect of certain commonly prescribed drugs. Cholesterol-lowering drugs and the cholesterol-lowering supplement nicotinic acid (niacin) can cause dry skin. Drugs classified as retinoids can also cause dry skin. These drugs include isotretinoin (Accutane), which is prescribed for acne, and etretinate, which is prescribed for psoriasis. Dry skin can also be a side effect of diuretics.
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