Frequency: from 1-20% of anaphylactic reactions (pretest probability)
Risk factors for occurrence:
(1) continued exposure to allergen, typically after an oral administration
(2) concurrent therapy with a beta-blocker
(3) occurrence of hypotension or laryngeal edema during the initial event (more serious reaction)
(4) delayed appearance during the first event (> 30 minutes after administration of allergen)
(5) inadequate therapy for the initial event
Clinical features of the second event:
(1) The second event may be of any severity and can be fatal.
(2) Usually the second event occurs within 8 hours of the first event's resolution but it can occur up to 78 hours afterwards. This means that the patient should be observed and have access to emergency supplies for up to 4 days after the event.
