Abstract

16.4% (95% CI, 15.3-17.7) of reported biphasic responses occurred. Biphasic reactions were reported by a total of 21.8% of self-respondents (95% CI, 19.7-23.8) and 12.8% of parent or guardian respondents (95% CI, 12.5-14.3) during their most recent food-allergic reaction. Compared to 30% of those who experienced a very severe initial reaction, 7.4% of those who experienced a mild initial reaction did so. When the initial reaction was light, 52.0% of self-respondents (95% CI, 38.0-35.7) and 69.6% of parent or guardian respondents (95% CI, 47.2-85.4) reported a mild secondary reaction. 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 when the original reaction was very severe. Increased probabilities of a biphasic reaction were linked to female sex, Black race, reaction age 5–12 and 26–66 years, first moderate, severe, or very severe reaction, and one or more yearly reactions.