Frequency and development of hen's egg allergy in early childhood in Germany: The EuroPrevall birth cohort.

Background: The occurrence of food allergy has been increasing in the perception of both parents and paediatricians. However, true incidence and tolerance development are unclear due to a lack of good quality population- based studies. Our aim was to determine the frequency and development of hen's egg allergy during early childhood with the best diagnostic standard. Methods: For the German study center of the EuroPrevall birth cohort we included consecutively 1,570 healthy newborns from 4 Berlin university and academic teaching hospitals. Using a standardized questionnaire we interviewed the parents face-to-face at birth and after 12, 24 and 30 months by telephone. Symptomatic children were examined in the study center including double-blind placebo-controlled food challenges if food allergy was suspected. Results: 1,321 of 1,570 children (84.1%) completed the 24-months followup. In 12 children (8 boys and 4 girls) hen's egg allergy was confirmed. We estimated the 2-year hen's egg allergy incidence at 1.89% (95%-CI 1.28% - 2.69%) after correcting for eligible children whose parents refused food challenge tests. One year after the confirmed diagnosis 5 of the 12 children tolerated hen's egg, whereas 3 children were still allergic. The parents of the 4 remaining children re-jected a second challenge test. Conclusions: The incidence of confirmed hen's egg allergy during the first 2 years of life was almost 2% in Berlin children. Approximately half of these children tolerated hen's egg 1 year later. In order to again assess the allergy status of all children, follow-up examinations at school age are planned