Food Allergy Research

New Study Identifies Predictors of Biphasic Allergic Reactions

Do you know what to look out for in the hours after an anaphylactic reaction? In some cases after anaphylaxis, there can be a second wave of symptoms that occurs hours or even days later without another exposure to an individual’s food allergen. This is known as a biphasic reaction, and a new study conducted by the Children’s Hospital of Eastern Ontario (CHEO) Research Institute aimed to identify the frequency and predictors of biphasic reactions.

biphasic allergic reactions

The study, “Epidemiology and clinical predictors of biphasic reactions in children with anaphylaxis,” was published last month in the Annals of Allergy, Asthma & Immunology and is the first to look at predictors of biphasic reactions among children. Of 1,749 patients presented to the pediatric emergency department, 484 satisfied the diagnostic criteria of anaphylaxis. Of these patients, 15 percent experienced a biphasic reaction and half of those required epinephrine.

The study concluded that the more severe the reaction, the more likely that a biphasic reaction will occur.

Researchers identified a number of evidence-based predictors of biphasic reactions, including:

  • a higher incidence in children ages 6 to 9;
  • treatment of the initial allergic reaction with more than one dose of epinephrine;
  • and a delay in epinephrine administration or arriving at the emergency department more than 90 minutes from the onset of the initial allergic reaction.

The study’s finding that anaphylaxis was more severe if epinephrine was given more than 90 minutes after the first symptoms reinforces the critical need for immediate use of epinephrine to reduce the symptoms of anaphylaxis. The authors emphasized that children with severe initial reactions appear more likely to develop biphasic reactions, and in particular, would benefit from a prolonged period of observation.

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