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Characteristics of tree nut challenges in tree nut allergic and tree nut sensitized individuals
Christopher Couch1, Tim Franxman2, Matthew Greenhawt3
1Division of Allergy and Clinical Immunology, The University of Michigan Medical School, Ann Arbor, Michigan; Allergy Asthma Clinic, Ltd, Phoenix, Arizona.
Background:
Characteristics and outcomes of tree nut (TN) oral food challenges (OFCs) in patients with TN allergy or sensitization alone are poorly studied.
Objective:
To determine the relation between TN sensitization levels and OFC outcomes.
Methods:
Open TN OFCs performed from 2007 through 2015 at a referral center were analyzed to compare outcome based on skin prick test (SPT) wheal size, food-specific immunoglobulin E (sIgE), peanut co-allergy, and TN sensitization only vs TN allergy with sensitization to other TNs. Delayed OFC was defined as longer than 12 months from the time of an sIgE level lower than 2 kUA/L.
Results:
Overall passage rate was 86% for 156 TN OFCs in 109 patients (54 almond, 28 cashew, 27 walnut, 18 hazelnut, 14 pecan, 13 pistachio, and 2 Brazil nut). Passage rates were 76% (n = 67) in patients with a history of TN allergy who were challenged to another TN to which they were sensitized and 91% (n = 65) in those with TN sensitization only (mean sIgE 1.53 kUA/L; range 0.35-9.14). Passage rates were 89% (n = 110 of 124) for a TN sIgE level lower than 2 kUA/L and 69% (11 of 16) for a TN sIgE level of at least 2 kUA/L. In 44 challenges in patients with peanut allergy and TN co-sensitization, the TN OFC passage rate was 96%. In 41 TN OFCs with a TN SPT wheal size of at least 3 mm, 61% passed, with a mean wheal size of 4.8 mm (range 3-11) in those passing vs 9 mm (range 3-20) in those failing.
Conclusion:
TN challenges are frequently passed in patients with TN sensitization with or without a history of TN reactivity despite a TN SPT wheal of at least 3 mm or a TN sIgE level of at least 2 kUA/L. Nearly all patients with peanut allergy and TN co-sensitization passed the TN challenge, questioning the clinical relevance of "co-allergy."