Biphasic Anaphylaxis


Biphasic anaphylaxis is an anaphylactic episode followed by an asymptomatic period with the return of anaphylactic symptoms in the absence of further exposure to the triggering antigen. The incidence of secondary reaction following primary anaphylactic reaction can range from 1% to 23% and occurs in up to 23% of adults and up to 11% of children. The time interval from primary to secondary reaction ranges from 1 to 72 hours, though predominantly occurs within 8 hours of the primary event.