Background: Atopic dermatitis (AD) has increased in prevalence in many countries in recent decades, but the risk factors for AD in developing countries are unknown. Helminthic parasites may play a role in protecting against allergic disease, but few studies have investigated the association of AD with parasitic infection.
Objective: To establish the independent effects of parasitic infection and other early life factors on the risk of AD in Ethiopia.
Methods: We conducted a cross-sectional survey and nested case-control study of children age 1 to 5 years in Jimma and surrounding rural areas in southwest Ethiopia. Cases were defined according to the International Study of Asthma and Allergies in Childhood criteria for AD and confirmed by clinical examination. Information on lifestyle and other potential risk factors was collected by parental questionnaire, and stool samples were analyzed for parasites.
Results: Complete data were obtained on 306 AD cases defined by International Study of Asthma and Allergies in Childhood criteria (prevalence, 4.4%) and 426 controls. There was no reduction in the risk of AD in relation to intestinal parasite infection; in fact, AD was increased in subjects with Trichuris (1.61; 95% CI, 1.14-2.26). The risk of AD was also unrelated to family size, crowding in the home, or breast-feeding, but was related to previously unrecognized factors including malaria and access to piped drinking water. Similar findings were apparent in cases and controls confirmed by clinical examination.
Conclusion: Neither intestinal parasite infection nor other proposed risk factors for AD appear to be related to the presence of the condition in young children in Ethiopia, suggesting that other factors may be more important in this population.