Risk factors for food allergy in an era of early allergen introduction

Published online July 9, 2024

Feeding infants common allergy-causing foods in the first year of life is recommended in many international guidelines for food allergy prevention. Most parents in Australia now introduce peanut and egg into their infant’s diet in the first year of life, with around half introducing these foods by age 6 months. However, some infants react on their first exposure to a food, even when this exposure occurs before age 6 months. Understanding how common food allergy is in a period where early allergen introduction is the norm and understanding risk factors for developing food allergy despite early introduction are critical next steps for food allergy prevention.  

In a recent issue of The Journal of Allergy and Clinical Immunology: In Practice, Soriano et al. describe new findings from the population-based EarlyNuts study in Melbourne, Australia. EarlyNuts recruited 1,933 12-month-old infants from council-run immunization sessions between 2017-2019, after infant feeding guidelines recommending introduction of common allergy causing foods in the first year of life were introduced. Infants had allergy tests (skin prick tests) to four foods (peanut, cashew, egg white, cow’s milk) and infants with evidence of sensitization were offered oral food challenges. Parents completed questionnaires which captured information on the infant’s diet and demographic and environmental exposures that may relate to food allergy risk.

A total of 1,420 infants had skin prick tests and were included in the present analysis. Most infants were introduced to peanut, egg, and cow’s milk by age 12 months. Around half were introduced to egg and peanut and three quarters to milk by 6 months. By contrast, only 8% had eaten cashew by 6 months, increasing to 25% by 12 months. The prevalence of allergy to any of the 4 foods tested was 11.3% and 2.8% of infants had multiple food allergies. Egg allergy was the most common (9.0%) followed by peanut (3.2%), cashew (1.5%), and cow’s milk (1.3%).

Infants who developed food allergy despite being fed the allergen by age 6 months were more likely to have Asian-born parents. Early-onset, moderate or severe eczema was associated with a higher risk of having food allergy, irrespective of what age allergens were introduced into the diet. Among infants who were eating peanut products by age 6 months, antibiotic use during that time increased the likelihood of having a peanut allergy. Associations with pet ownership were mixed; having pet dogs was associated with a reduced likelihood of egg allergy among infants who were introduced to egg later (after 7 months), and cat ownership was associated with an increased likelihood of peanut allergy among infants introduced to peanut early.

In a cohort of babies in which early allergen introduction was common, the prevalence of food allergy was still high. It was also remarkably similar to results reported from the HealthNuts study, consisting of infants from the same region born between 2006-2010, when allergen avoidance was widespread. 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 preventable with early allergen introduction.

The Journal of Allergy and Clinical Immunology: In Practice is an official journal of the AAAAI, focusing on practical information for the practicing clinician.

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