In A Nutshell – Birch Co-sensitization Among Children With Peanut, Hazelnut And Almond Allergies.

Abstract

The Hospital for Sick Children, 5 Montreal Children. RATIONALE: Birch allergy affects up to a third of Canadians (Lok et al J Asthma 2017). Cross reaction between birch pollen and certain tree nut allergens mainly hazelnut may contribute to false positive skin tests as well as pollen-food syndrome and mislabeling patients as having a lifethreatening allergy to hazelnut. We aimed to determine the usefulness of double-blind, placebo-controlled food challenge (DBPCFC) in the diagnosis of primary hazelnut allergy (HA) in our oral immunotherapy study cohort. METHODS: We conducted DBPCFC in 9 children (median age 15, and IQR 9-17) with previous history of an IgE-mediated reaction to hazelnut with positive skin test and/or specific IgE (sIgE) as well as 22 children (median age 12, IQR 10-14) with peanut allergy (PA) referred by allergists as controls because cross-reaction with common allergens like birch pollen in PA is less likely. Four HA children and 11 PA children were male. Additional patient demographics, skin prick test, sIgE, and adverse events were also documented. Fisher's exact test was used for analysis of binary variables. RESULTS: Six out of 9 HA patients tolerated DBPCFC while no PA patient did (P<0.001). Adverse reactions were mild in the hazelnut challenge with no use of epinephrine. In contrast, anaphylactic adverse reactions (> _ 2 organ systems involved) occurred to 21 PA patients with epinephrine use in 16 out of 22 patients (P<0.05). CONCLUSIONS: DBPCFC is required for the diagnosis of HA and hazelnuts are less likely to cause severe allergic reactions compared to peanuts. Tree nut allergy needs to be investigated individually.