The prevalence of allergy to egg: a population-based study in young children

Background: The aim of the present study was to estimate the prevalence of adverse reactions to egg, as population-based prevalence estimates based on objective diagnostic procedures are lacking. Methods: The parents of 2721 children in a population-based birth cohort completed questionnaires on the occurrence of any reaction to food at 12, 18, and 24 months of age. Children with parentally reported reactions to eggs at the age of 2 years were selected for further examination. A stepwise diagnostic procedure was developed that included diet trials at home, skin prick tests, and open and double-blind, placebo-controlled food challenges. The mean age of the children at the time of the examination was 2.5 years (CI 2.5-2.6). A sample of children without perceived reactions to egg was also selected for assessment of unrecognized reactions. Results: The estimated point prevalence of allergy to egg in children aged 2 1/2 years was 1.6% (CI 1.3-2.0%), with an upper estimate of the cumulative incidence by this age calculated roughly at 2.6% (CI 1.6-3.6). Almost all reactions were IgE mediated. In general, two-thirds of the parentally perceived reactions were verified. However, the positive predictive value of a parentally perceived reaction depended on the number of times it had been reported, and increased from 50% to 100%, for reactions reported one and three times, respectively. Unrecognized reactions were infrequent. Conclusions: This study confirms that allergy to egg is frequent in a child population.