Influence of early day-care exposure on total IgE levels through age 3 years

Background: Early day care is inversely associated with asthma and atopy in later childhood, but its association with early immunologic markers of asthma risk is not known. Objective: We sought to assess the relation of day care by 3 months to total IgE levels through age 3 years. Methods: Day care was assessed prospectively among 362 nonselected infants enrolled in the Infant Immune Study. Children were categorized based on day-care status by 3 months of age as follows: no day care, day care inside the home with other children, day care outside the home with no other children, or day care outside the home with other children. Total IgE levels were measured in blood obtained at 3, 12, 24, and 36 months. Relations between day care and IgE levels were assessed at each age and longitudinally, with stratification by maternal asthma and atopy. Results: Day care by 3 months was associated with decreased IgE levels through age 3 years (coefficient: -0.19 log IU/mL, P = .001). The greatest effect was evident for children cared for outside the home. Stratified analyses indicated that the relation existed primarily among children who had atopic or asthmatic mothers. Day-care entry after 3 months showed no relation with IgE levels. Conclusion: Day-care attendance by 3 months is associated with decreased total IgE levels in the first 3 years of life in children of mothers who are atopic, asthmatic, or both. Clinical implications: Early day-care exposure can reduce IgE levels, which in turn might reflect a reduced risk of allergic disease in predisposed children.