Patterns of Tree Nut Sensitization and Allergy in the First 6 Years of Life in a Population–Based Cohort

Abstract

To determine the prevalence of tree nut allergy at age 6 years and investigate the relationship between egg and peanut allergy at age 1 year and tree nut allergy at age 6 years to guide testing and introduction advice.This study included infants recruited between 11 and 15 months for the longitudinal HealthNuts study in Melbourne, Australia.At entry, all subjects underwent skin prick testing (SPT) to egg, peanut, and sesame. At age 1 year, egg and peanut allergy were determined by oral food challenge. SPT to tree nuts (almond, cashew, hazelnut) was performed, and parental history of symptoms with tree nut ingestion was obtained. Those with negative SPT results were advised to introduce tree nuts at home; avoidance was recommended for those with positive SPT results. At age 6 years, a questionnaire was administered, SPT was performed, and tree nut allergy was assessed by food challenge.Five thousand two hundred seventy-sixchildren participated in the HealthNuts study at age 1. One thousand one hundred fourteen (21%) underwent additional evaluation, including SPT for tree nuts. At age 1 year, 6 parents (0.1%) reported a history consistent with tree nut allergy. Among those with challenge-confirmed egg or peanut allergy at age 1 year, 41% were already sensitized to 1 or more tree nuts, with an even higher rate in those with both allergies. At age 6, the prevalence of tree nut allergy was 3.3%, with cashew being the most common trigger, followed by hazelnut and almond. Forty-three percent of those with any tree nut allergy had peanut allergy. Of those with peanut allergy, 45% reacted to 1 or more tree nuts, most commonly cashew. In examining predictors of tree nut allergy, 14% of those with egg allergy at age 1 year, 27% of those with peanut allergy at age 1, and 37% of those with both egg and peanut allergy at age 1 had tree nut allergy at age 6 years.There is a low parent-reported rate of tree nut allergy at age 1 year, likely due to low tree nut consumption in the first year of life. However, 33% of those with peanut allergy and 41% of those with peanut or egg allergy are already sensitized to 1 or more tree nuts at age 1, with a higher rate in those with allergy to both foods. More than one-third of those with tree nut sensitization at age 1 are allergic to 1 or more tree nuts at age 6. Almost half of those with both peanut and egg allergy at age 1 have tree nut allergy at age 6. The prevalence of tree nut allergy at age 6 (3.3%) is similar to that of peanut allergy (2.8%), with cashew being the most common tree nut allergen.This study reports a high rate of tree nut sensitization and potential for allergy in those with egg and/or peanut allergy at age 1 and highlights the need to investigate the best approach to tree nut evaluation in those with known food allergy as well as strategies to prevent tree nut allergy in this at-risk population.