Understanding about patient-reported biphasic food-related allergic reactions currently remains sparse.
To characterize patient-reported biphasic food-related allergic reactions among a national food allergy registry.
We utilized two Patient Registry surveys established by Food Allergy Research & Education (FARE). Variables were described with proportions and 95% confidence intervals; unadjusted results were stratified by respondent type. Multivariable logistic regression evaluated the adjusted odds of reporting a biphasic reaction.
The incidence of reported biphasic reactions was 16.4% (CI: 15.3-17.7). 12.8% (CI: 12.5-14.3) of parent/guardian respondents and 21.8% (CI: 19.7-23.8) of self-respondents indicated a biphasic reaction during their most recent food-allergic reaction. Among respondents with a mild initial reaction, 7.4% reported a biphasic reaction compared with 30% with a very severe initial reaction. When the initial reaction was mild, 69.6% of parent/guardian respondents (CI: 47.2 – 85.4) and 52.0% of self-respondents (CI: 38.0 – 35.7) with a biphasic reaction reported a mild secondary reaction. When the initial reaction was very severe, 36.3% of parent/guardian respondents (CI: 26.4 – 47.5) and 42.9% of self-respondents (CI: 31.1 – 55.5) with a biphasic reaction reported a very severe secondary reaction. Female gender, Black/African-American race, reaction age 5-12 and 26-66 years, initial moderate, severe, or very severe reaction, and one or more annual reactions were associated with increased odds of a biphasic reaction.
This study characterizes the incidence of patient-reported biphasic reactions and provides valuable information on probable severity of a biphasic food-related allergic reaction. Further research is necessary to understand the epidemiology of food-related biphasic reactions.

Copyright © 2021. Published by Elsevier Inc.