A Guide To Dry Skin Disorders In The Lower Extremity
At this wintry time of year, more patients may be presenting with cracked heels and itchy feet due to dry skin. Accordingly, this author discusses the diagnosis and treatment of different forms of dry skin, including dry skin concomitant with common diseases.
How many times a day do you see any of these conditions: stasis eczema, eczema, atopic dermatitis, contact dermatitis, xerosis, psoriasis or stucco keratosis? To some podiatrists, the skin is just a structure you have to get past in order to get to the bones. However, the skin problems are what bring patients into your office with symptoms like tightness, tingling, itchiness, burning, scaling, flaking and lichenification. When you cannot concentrate on your work because you are scratching, when your sleep is interrupted because of burning, when you have noticeable dry skin patches on your legs, then dry skin is in the fast lane.
Don’t look past the skin for other podiatric concerns. The skin can be a “mirror” of what is going on in the body. The lower legs and heel are notoriously problematic with dry skin symptoms. However, just because we do not treat the hands and forearms, we still need to evaluate those areas so we get the big picture. The feet do not exist in a vacuum.
The skin acts as a barrier and protects underlying tissues from infection, desiccation, chemicals and mechanical stress. Disruption of these functions results in increased transepidermal water loss and deceases in the stratum corneum’s water content, and is associated with conditions like atopic dermatitis, eczema, xerosis, contact dermatitis and other chronic skin diseases. Moisturizers can improve these conditions through restoration of the integrity of the stratum corneum, acting as a barrier to water loss and replacement of skin lipids and other compounds.1 Despite the knowledge of well recognized aggravating factors, the etiology of dry skin conditions is an enigma and the management of the condition is often suboptimal.2
In the foot and ankle region, we have three types of skin: plantar skin, which has no oil glands and the largest number of sweat glands anywhere; dorsal skin, which is normal skin; and the skin overlying the shin, which is the thinnest and more prone to injury.
Dry skin occurs when 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. The cells of the stratum corneum have lost their nucleus, are rich in keratin and are known as “corneocytes.”3 Intercellular lipids bind the corneocytes together. 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, skin requires a water content of 10 to 15 percent to remain supple and intact.4 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. The skin contains natural moisturizers: ceramides, glycerol, urea and lactic acid. These help rehydrate skin to prevent water loss, which is the reason that many of the products out on the market contain urea, lactic acid, salicylic acid and glycol. They are trying to “mirror” the skin. The essential ingredient of an emollient is lipid (fats, waxes and oils).5