Scientific Study

INTRODUCTION: Longitudinal population-based data regarding tree nut allergy are limited. OBJECTIVES: To determine population prevalence of tree nut allergy at age 6 years, and explore the relationship between egg and peanut allergy at age 1 year and development of tree nut allergy at age 6 years. METHODS: A population-based sample of 5,276 children were recruited at age one and followed up at age 6 years. At age 1 allergy to egg and peanut were determined by oral food challenge and parents reported their child's history of reaction to tree nuts. Challenge-confirmed tree nut allergy was assessed at age 6. RESULTS: At age 1, prevalence of parent-reported tree nut allergy was 0.1% (95% CI 0.04-0.2). Only 18.5% of infants had consumed tree nuts in the first year of life. At age 6, challenge-confirmed tree nut allergy prevalence was 3.3% (95%CI 2.8-4.0), with cashew the most common (2.7%, 95% CI 2.2-3.3). Of children with peanut allergy only at age 1, 27% (95%CI 16.1-39.7) were tree nut allergic at age 6, compared with 14% (95%CI 10.4-17.9) of those with egg allergy only and 37% (95%CI 27.2-47.4) of those with both peanut and egg allergy. CONCLUSIONS: Tree nut allergy is uncommon in the first year of life, likely due to limited tree nut consumption. At age 6 years, tree nut allergy prevalence is similar to peanut allergy prevalence. Over a third of children with both peanut and egg allergy in infancy have tree nut allergy at age 6. Understanding how to prevent tree nut allergy should be an urgent priority for future research.