Natural history of allergic sensitization in infants with early-onset atopic dermatitis: results from ORCA Study.

BACKGROUND Early-onset atopic dermatitis (AD) is a particular phenotype that may convey a risk of developing multiple sensitizations to allergens but little is known about the pathway of sensitization. The aims of this study were to describe the natural history of sensitization to allergens for this phenotype and to identify the most predictive marker associated with the risk of developing sensitization to inhaled allergens in a well-selected cohort of infants with AD. METHODS Infants with active AD were enrolled and prospectively explored for biological markers of atopy every year until the age of 6 yr. Allergic sensitization was defined as the presence of positive specific IgEs to allergens and multiple sensitizations as being sensitized to ≥2 allergens. Elevated blood eosinophilia was defined as an eosinophil blood count ≥470 eosinophils/mm(3) and elevated total IgE as a serum IgE level ≥45 kU/l. RESULTS Two hundred and twenty-nine infants were included. Elevated blood eosinophilia was observed at baseline in 60 children (26.2%) and elevated total IgE in 85 (37.1%). When elevated at baseline, eosinophilia and IgE levels remained significantly higher during the follow-up period. Sensitization to food allergens decreased from 58% to 34%, whereas sensitization to inhaled allergens increased over time from 17% to 67%. Initial multiple sensitizations to food allergens were the most predictive factor for the risk of developing sensitization to inhaled allergens at 6 yr (OR 3.72 [1.68-8.30] p < 0.001). CONCLUSIONS In the early-onset AD phenotype, multiple sensitization to food allergens conveys a higher risk of sensitization to inhaled allergens than single sensitization.