Egg Allergy Prevalence Before and After Guidelines for Earlier Egg Introduction

Importance: Egg allergy is among the most common food allergies in infants. Allergy prevention guidelines have been updated globally based on evidence that earlier egg introduction reduces the risk of egg allergy, and these guidelines have been adopted widely. However, the association of this guideline change with the prevalence of egg allergy is unclear. Objective: To estimate the change in population prevalence of egg allergy after a guideline update recommending earlier introduction of egg into the infant diet. Design, Setting, and Participants: This cross-sectional study included infants aged 11 to 15 months in 2 population-based samples, recruited using identical methods when attending their 12-month immunization visit at immunization centers in Melbourne, Australia, before (2007-2011) and after (2018-2019) an update to allergy prevention guidelines. To isolate an association between a change in prevalence of egg allergy and the guideline change, direct regression standardization was used to estimate prevalence in the 2018-2019 sample had the distribution of known risk factors remained the same as in the 2007-2011 sample. Multiple imputation was used to address missing data. Prespecified subgroup analyses were conducted for infants with early eczema and stratified by parent country of birth. Data were analyzed between March 2025 and March 2026. Exposures: Data on demographics, food allergy risk factors, egg introduction, and reactions were collected via questionnaires. Main Outcome and Measures: Infants underwent skin prick tests to egg, and those with positive results underwent oral food challenges. Results: A total of 7209 of 9500 eligible infants were included from 2 cohorts: 5276 infants (median [IQR] age, 12.4 [12.2-12.9] months; 50.8% [2665 of 5244] males; response rate, 76% [5276 of 6957]) from the 2007-2011 cohort and 1933 infants (median [IQR] age, 12.5 [12.2-13.0] months; 51.8% [1001 of 1932] males; response rate, 76% [1933 of 2543]) from the 2018-2019 cohort. The median (IQR) age at egg introduction decreased from 8 (6-10) months in 2007-2011 to 6 (6-8) months in 2018-2019. After adjusting for known allergy risk factors, the prevalence of egg allergy decreased from 9.2% in 2007-2011 to 7.6% in 2018-2019 (adjusted absolute difference, -1.6 [95% CI, -3.3 to -0.005] percentage points). In infants with early eczema, egg allergy decreased from 34.6% to 21.9% (adjusted absolute difference, -12.7 [95% CI, -20.0 to -5.4] percentage points). Conclusions and Relevance: This study provides population-level evidence that updated infant feeding guidelines recommending earlier introduction of egg led to measurable reductions in the population prevalence of egg allergy. The findings suggest that guideline updates informed by randomized trial evidence may be associated with a reduction in food allergy prevalence when implemented effectively.