Atopic dermatitis : Clinical and epidemiological aspects in children up to four years

Abstract: Atopic dermatitis (AD) is a pruritic, chronically relapsing inflammatory skin disease; its aetiology is presumed to be multifactorial with interactions between genetic and environmental factors. In recent decades the prevalence of AD has increased remarkably, most likely due to environmental factors in early life. While AD usually presents in the first year, few prospective cohort studies have focused on young children with AD. The present overall objective was to study, prospectively, different aspects of AD in very young children from a community birth cohort of 4089. Two hundred and twenty-one children with AD from the cohort were followed consecutively and clinically from onset of AD. At 2 years they were examined concerning Hanifin's and Rajka's criteria for AD, eczema severity and atopic sensitisation (skin prick test to foods, Phadiatop). Mild-to-moderate eczema predominated, and the majority (67%) were not sensitised. Eczema severity did not differ between sensitised and non-sensitised children. Xerosis, course influenced by environmental factors, and facial erythema, were the only signs meeting the minor criteria in more than 50% of patients, and these therefore seem the most useful in diagnosing AD at two years of age. Using annual questionnaires, we studied the cumulative incidence of AD, other atopic disease manifestations and infections in the cohort. Atopic diseases in parents and siblings and exposure to certain environmental factors were also recorded. The occurrence of serum IgE antibodies to inhalant and food allergens was analysed at 4 years of age, and AD was divided into IgE-associated AD and nonIgE-associated. Already during the first two years, there was a significant association not only between AD and other atopic disease manifestations; but also between AD and respiratory infections manifested in an increased rate of acute otitis media, pneumonia and use of antibiotics. There was a higher proportion of atopic disease manifestations, but not respiratory infections, in children with onset of AD during the first year of life than during the second. Cumulatively up to 4 years of age, 33% reportedly had AD: 27. 1 % of the children without parental atopic history, 37.9% of those with single parental atopic history and 50.0% with double parental atopic history. The effects of parental history of eczema and of atopic respiratory disease did not differ significantly, nor did those of matemal history and of paternal. Parental eczema was a risk factor for AD irrespective of its association with IgE, but parental history of atopic respiratory disease mainly increased the risk of IgE- associated. AD. The effect of three recommendations (to breast-feed exclusively for at least 4 months, and to avoid parental smoking and furred pets at home) from the Swedish national guidelines for the prevention of "allergy and atopic disease" on the development of AD up to 4 years was investigated. Even in families with double atopic heredity, 42% missed out on at least one of these three recommendations. Following the Swedish national guidelines concerning breast-feeding, smoking and furred pets at home had little effect on the cumulative incidence of AD, nor on IgE-associated AD or non-IgE-associated AD, up to 4 years of age. Since the risk factors for AD and other atopic diseases seem to differ, future studies focusing on AD are required for the development of measures for its primary prevention.