Infant formula introduced within 24 hours of birth increases egg allergy risk.

BACKGROUND: Breast secretions of colostrum precede milk production in the first few days after birth, providing nutrition and playing a critical role in shaping the newborn's gut microbiome and immune system development. Infants fed commercial milk formula in the first few days consume less colostrum, and previous studies have found an associated increased risk of food allergy. OBJECTIVE: To determine the risk of food allergen sensitization and IgE-mediated food allergy development in infants who received any formula during their first 3 days of life. METHODS: In a high-risk (defined by family history) cohort of 563 infants, born at 37 weeks' gestation or later, early-life infant feeding practices data were prospectively collected. At age 1 year, infant IgE-mediated food allergy, food allergen sensitization, and medically diagnosed eczema were assessed. RESULTS: In their first 3 postnatal days, 36.8% (207 of 563) of infants received formula, with 21.8% (123 of 563) of infants receiving formula within 24 hours of birth. Overall, 3.4% of infants developed egg allergy, despite timely egg introduction in the infant diet at age 6 months. There was an increased risk of egg allergy (adjusted odds ratio, 3.62; 95% CI, 1.29-10.16; P = .014) and egg sensitization (adjusted odds ratio, 2.50; 95% CI, 1.09-5.74; P = .031) following formula introduction within 24 hours of birth. No associations were found with other food allergies or sensitization, but there were only a few cases. CONCLUSIONS: Along with timely infant diet food allergen introduction, avoiding formula supplementation especially within 24 hours of birth is another potential food allergy prevention strategy that warrants further investigation in randomized trials.