Biphasic Anaphylaxis: Epidemiology, Predictors, and Management

Abstract

Anaphylaxis is the most severe form of allergy that rapidly affects multiple body systems and can be deadly. The pattern of an anaphylactic reaction can be uniphasic (or monophasic), biphasic (also called delayed or late phase), or refractory in nature. Most anaphylactic reactions are uniphasic, with early allergic responses that occur minutes after exposure and typically subside with time without recurring. However, some have biphasic responses. The most widely cited definition of biphasic anaphylaxis is recurrence of anaphylactic symptoms after initial resolution, despite no further exposure to the trigger. Owing to concerns about potentially fatal biphasic reactions, most guidelines recommend a prolonged period of observation and monitoring after treatment of the initial reactions, to increase detection of biphasic anaphylaxis. In this chapter, we summarize the existing literature on the epidemiology and predictors of BA and provide guidance for post-anaphylaxis care and monitoring.