Volume 99, Issue s3

Urticaria and angioedema are common-and commonly frustrating-problems for physicians and patients alike. Patients often are in considerable distress with pruritus and uncomfortable lesions. They are frightened about their condition and frustrated when modem medicine cannot pinpoint the cause of the symptoms. Both urticaria and angioedema may be categorized as acute and chronic conditions. The dividing line between acute and chronic forms is relatively arbitrarily set at 6 weeks. A thorough history and physical examination may provide clues to the underlying cause, but in the majority of patients, the cause is rarely identified. One is more likely to discover the cause of acute than of chronic urticaria. A multitude of laboratory tests can be performed, but they often do not provide a diagnosis. It is not appropriate to do a large "screening" battery oflaboratory tests. The dermal mast cells and their mediators playa central role in chronic urticaria. Chronic urticaria may have an autoimmune aspect. Recent evidence reveals that 50% of patients with chronic urticaria have a cutaneous autoimmune disorder mediated by autoantibodies to the high-affinity IgE receptor on mast cells. Biopsy may be necessary and may help with treatment.

Atopic dermatitis is a common disease, causing significant morbidity. The histology and cellular mechanisms suggest that atopic dermatitis is an atopic disease similar to asthma and allergic rhinitis, with helper T type 2 lymphocytes being atleast a component of the pathogenesis of the disease. Specific allergies, including food allergies, should be explored and treated. Treatment should be directed at increasing the patient's quality of life. Antihistamines, topical steroids, and lubricants are the keystones of therapy. In severe cases, oral steroids may be necessary but should be used sparingly. Interferon, cyclospocine, phototherapy, and immunosuppressive agents may be necessary in refractory cases. It appears that leukotriene inhibitors may have a future role in therapy. Clinical assessment and follow-up are important, as other atopic diseases such as asthma and allergic nasosinus disease may eventually develop in many of these patients.

Contact dermatitis is a common condition that can be categorized as irritant dermatitis and allergic contact dermatitis. Although each of these conditions may have a similar presentation, allergic contact dermatitis is immunologically mediated, whereas irritant contact dermatitis is not. Contact dermatitis can be acute, subacute, or chronic, and each of these phases may progress into the next. Almost anysubstance may induce a cutaneous reaction, depending on its concentration, the duration of contact, and the condition of the contacted skin. It is estimated that there are more than 6 million chemicals in the environment; approximately 3000 are potential sensitizers. A careful history may identify the responsible agent. If the contactant is identified and eliminated, the contact dermatitis can be a self-limited,mild condition. H the exposure is not discontinued, a cycle of itching, scratching, and skin disruption occurs, which leads to chronic changes in the skin. The history of presentation, including occupational exposures, and distribution of the rash are important in identifying the offending agent. More severe cases may require more extensive evaluation, possibly including patch testing, to determine the offending agent. This article reviews treatment, including antihistamines, topical and oral steroids, physical measures such as cold water compresses, and the treatment of secondary infection.

The role of dietary factors in chronic skin diseases has been a subject of controversy, but several investigators have shown the effectiveness of elimination diets in the management of some patients with atopic dermatitis. Chronic skin diseases are common, complex, and often difficult to treat; therefore, the physician should consider all possible causes. More people consider themselves to have food allergies than can actually be documented to have an immunologic reaction to foods. Six foods--egg, peanut, cow's milk, soy, fish, and wheat-account for most skin reactions to food in children, with egg, peanut, and cow's milk being most common. Elimination of the offending food can be an effective form of treatment, but it must be done with caution, and while ensuring that the patient maintains adequate nutrition.