Atopic dermatitis usually starts after 2 months of age, and the majority of patients who develop the rash do so by the age of 5. Nine out of ten children will outgrow the disease by their teens, but symptoms can persist into adulthood. Men and women are equally affected. The most distressing symptom is severe itching, which can interfere with the patient’s sleep as well as daytime performance at school and work.
The cause of the disease is unknown, although disturbances of the immune and vascular systems have been suggested by researchers. Genetics may also play an important role: family members of patients with atopic dermatitis often have a history of allergic respiratory disease such as asthma or allergic rhinitis. The rash appears differently according to age. Infants tend to suffer from oozing vesicles and crusting on the head and diaper area, which occur with subacute onset. Older children and adults experience a chronic rash characteristically on the inner surface of the elbows (antecubital fossa) and the back of the knees (popliteal fossa). Other affected areas include the neck, face, and upper chest and are usually symmetric on both sides of the body. The hallmark of chronic atopic dermatitis is “lichenification” of the skin: it is thickened, more darkly pigmented than the rest of the body, with accentuated skin fold markings.
The disease has an overall chronic course punctuated by acute flare-ups. These flare-ups are thought to be triggered by food allergy, skin infections, irritating chemicals, climate changes, and emotional stressors. The most frequent complication of atopic dermatitis is secondary infection of the rash by a bacteria (Staphylococcus aureus) or a virus (herpes simplex, variola, vaccinia virus). These secondary infections must be promptly treated with the appropriate agent.
