Patterns of tree nut sensitization and allergy in the first 6 years of life in a population-based cohort

Background: Longitudinal population-based data regarding tree nut allergy are limited. Objectives: We sought to determine the 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 5276 children was recruited at age 1 year and followed up at age 6 years. At age 1 year, allergies to egg and peanut were determined by means of 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 years. Results: At age 1 year, the prevalence of parent-reported tree nut allergy was 0.1% (95% CI, 0.04% to 0.2%). Only 18.5% of infants had consumed tree nuts in the first year of life. At age 6 years, challenge-confirmed tree nut allergy prevalence was 3.3% (95% CI, 2.8% to 4.0%), with cashew the most common (2.7%; 95% CI, 2.2% to 3.3%). Of children with peanut allergy only at age 1 year, 27% (95% CI, 16.1% to 39.7%) had tree nut allergy at age 6 years compared with 14% (95% CI, 10.4% to 17.9%) of those with egg allergy only and 37% (95% CI, 27.2% to 47.4%) of those with both peanut and egg allergy. Conclusions: Tree nut allergy is uncommon in the first year of life, likely because of limited tree nut consumption. At age 6 years, tree nut allergy prevalence is similar to peanut allergy prevalence. More than a third of children with both peanut and egg allergy in infancy have tree nut allergy at age 6 years. Understanding how to prevent tree nut allergy should be an urgent priority for future research.