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Atopic dermatitis (AD) is a chronically relapsing skin disease that occurs most commonly during early infancy and childhood. It is frequently associated with abnormalities in skin barrier function, allergen sensitization, and recurrent skin infections. There is no single distinguishing feature of AD or a diagnostic laboratory test. Thus, the diagnosis is based on the constellation of clinical findings listed in Table 14-1.1
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Since the 1960s, there has been a more than threefold increase in the prevalence of AD.2 AD is a major public health problem worldwide, with a prevalence in children of 10–20% in the United States, Northern and Western Europe, urban Africa, Japan, Australia, and other industrialized countries.3 The prevalence of AD in adults is approximately 1–3%. Interestingly, the prevalence of AD is much lower in agricultural regions of countries such as China and in Eastern Europe, rural Africa, and Central Asia. However, the most recent data from the International Study of Asthma and Allergies in Childhood (ISAAC) Phase Three study confirms that AD is a disease with high prevalence, affecting patients in both developed and developing countries.4 There is also a female preponderance for AD, with an overall female/male ratio of 1.3:1.0.
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The basis for this increased prevalence of AD is not well understood. However, wide variations in prevalence have been observed within countries inhabited by similar ethnic groups, suggesting that environmental factors are critical in determining disease expression. Some of the potential risk factors that may be associated with the rise in atopic disease include small family size, increased ...