Characterizing Biphasic Food-Related Allergic Reactions Through a US Food Allergy Patient Registry

Background: Understanding about patient-reported biphasic food-related allergic reactions is currently sparse. Objective: To characterize patient-reported biphasic food-related allergic reactions among a national food allergy registry. Methods: We used two patient registry surveys established by Food Allergy Research and Education. Variables were described with proportions and 95% confidence intervals (CIs); unadjusted results were stratified by respondent type. Multivariable logistic regression evaluated the adjusted odds of reporting a biphasic reaction. Results: The incidence of reported biphasic reactions was 16.4% (95% CI, 15.3-17.7). A total of 12.8% of parent or guardian respondents (95% CI, 12.5-14.3) and 21.8% of self-respondents (95% CI, 19.7-23.8) 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 or guardian respondents (95% CI, 47.2-85.4) and 52.0% of self-respondents (95% 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 or guardian respondents (95% CI, 26.4-47.5) and 42.9% of self-respondents (95% CI, 31.1-55.5) with a biphasic reaction reported a very severe secondary reaction. Female sex, Black 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. Conclusions: This study characterizes the incidence of patient-reported biphasic reactions and provides valuable information on the probable severity of a biphasic food-related allergic reaction. Further research is necessary to understand the epidemiology of food-related biphasic reactions.