Xerosis is the term used to describe a condition where there is a rough, dry textural feel to the skin, accompanied by fine scaling and sometimes fine fissuring. Increasing xerosis is usually accompanied by increasing itch. It is a descriptive term, not a diagnosis. It may result from a combination of environmental conditions (low humidity, degreasing of the skin by excessive bathing, soap or detergent use), genetic disorders of keratinization (ichthyoses), Down’s syndrome (12% of patients), atopic eczema (where it may be a manifestation of a fillagrin mutation), endocrine disease states (hypothyroidism), diabetes mellitus (39% of patients), celiac disease, and a host of underlying disease states such as chronic renal failure, liver disease (including 69% of patients with primary biliary cirrhosis), malnutrition, anorexia nervosa (58% of patients), essential fatty acid deficiency, Sjögren syndrome (56% of patients), HIV infection, lymphoma (where it may result in an acquired ichthyosis), and carcinomatosis (especially hematologic). It is more common in the elderly. Drugs are occasionally implicated. It is reported to be more frequent in the winter.
Initial evaluation should seek to distinguish simple xerosis from a genetic ichthyosis, although management is similar for both conditions. Family history, distribution, and morphology will help to differentiate the two. A history of weight loss, diarrhoea, dietary history, and body mass index may give clues towards an underlying metabolic or malabsorptive disorder. Dry eyes and mouth may indicate underlying Sjögren syndrome. History and clinical examination should seek symptoms and signs of hypothyroidism, diabetes mellitus, and chronic renal disease. Drug use and sexual contact history may reveal HIV infection. Xerosis is an almost universal accompaniment of atopic eczema.
The mainstay of therapy for xerosis after any underlying disorders (if possible) are corrected are improvement of the humidity in the patient’s environment, avoidance of exacerbating factors such as soap and detergents, and the use of emollients or humectants.
Low environmental humidity both at home and work will exacerbate xerosis of any cause. Arid air is a problem in air-conditioned homes, offices, and vehicles. Hot dry air directed to the lower legs during the winter in the front of automobiles is a common cause of lower leg xerosis. In the home or workplace humidifiers can be fitted over radiators; alternatively, placing wet towels or containers of water over them will increase air humidity.
Soaps and detergents degrease the skin, reduce epidermal thickness, and increase scale and itch, and so are best avoided, and light emollient cleansers (soap substitutes) are suggested in their place. Bathing in tepid water is often preferred by patients, and patting the skin dry will produce less scale and dryness than vigorous toweling.
Emollients (which simply produce an impervious film over the epidermis and prevent ‘transpiration’) and humectants (such as lactic acid, urea, or glycerine that hold water in the epidermis osmotically) are the mainstays of therapy. Few good comparative studies exist for the most common type of xerosis, which is surprising because they are the most frequently used dermatological products. They should be used liberally and as frequently as possible and applied in the direction of hair growth; emollients are particularly valuable after bathing or showering to hold water in the epidermis. Light emollients for use in the shower or bath may be preferred to bath oils by some. Choice of emollient is entirely personal to the patient. A pack with small amounts of a variety of products for home trial or a self-selection ‘tub tray’ for the clinic is likely to enhance compliance.
Agents containing α-hydroxy acids (AHAs) may offer some advantages over conventional paraffin-based emollients, but this may be at the expense of irritation in some people. Low-concentration salicylic acid may help reduce scale in more severe xerosis, but it is essential to remember that systemic absorption and salicylism can occur.