Prevalence and Determinants of Food Allergy in the Era of Early Allergen Introduction: The EarlyNuts Population-Based Study.

Background: Infant feeding guidelines in Australia changed in 2016 to recommend introducing common allergy-causing foods by age 1 year to prevent food allergy. Although most Australian infants now eat peanut and egg by age 6 months, some still develop food allergy despite the early introduction of allergens.

Objectives: To describe the prevalence of food allergy in a cohort recruited after introducing the nationwide allergy prevention recommendations; identify characteristics of infants who developed allergy despite early introduction of allergens; and estimate the causal effect of modifiable exposures on food allergy prevalence and whether this differed between infants who were introduced to allergens before or after age 6 months.

Methods: We recruited a population-based sample of 12-month-old infants in Melbourne, Australia. Infants had skin prick tests to four foods and parents completed questionnaires. Infants with evidence of sensitization were offered oral food challenges. Prevalence estimates were adjusted using inverse probability weighting.

Results: In a cohort of infants (n = 1,420) in which nearly all infants had been introduced to common allergens such as egg, milk, and peanut by age 1 year, the prevalence of food allergy remained high at 11.3% (95% CI, 9.6-13.4). Infants who developed food allergy despite introduction of the allergen by age 6 months were more likely to have Asian-born parents. Early-onset moderate or severe eczema was associated with an increased odds of food allergy irrespective of whether allergens were introduced before or after age 6 months. Among infants who were introduced to peanut at age 6 months or earlier, antibiotic use by age 6 months was associated with an increased odds of peanut allergy (adjusted odds ratio = 6.03; 95% CI, 1.15-31.60).

Conclusions: In a cohort in which early allergen introduction was common, the prevalence of food allergy remained high. Infants who developed food allergy despite introduction of the respective allergen by age 6 months were more likely to have had Asian parents and early-onset eczema. New interventions are needed for infants with a phenotype of food allergy that is not amenable to early allergen introduction.