From the Guidelines
Allergic reactions can occur within minutes to several hours after exposure to an allergen, with severe reactions like anaphylaxis typically appearing within 5-30 minutes of exposure. The timing of an allergic reaction varies based on the type of reaction and individual sensitivity, with immediate reactions developing within seconds to minutes, and delayed reactions taking hours or even days to manifest 1. For instance, food-induced anaphylaxis is typically characterized by a rapid onset and evolution of symptoms over minutes to several hours, with deaths from food-induced anaphylaxis reported within 30 minutes to 2 hours of exposure 1. Some key points to consider about the timing of allergic reactions include:
- The time course of an anaphylactic reaction may be uniphasic, biphasic, or protracted, with uniphasic reactions resolving within the first minutes to hours, biphasic reactions recurring after apparent resolution of the initial reaction, and protracted reactions lasting for hours or days 1.
- Fatalities associated with food-induced anaphylaxis are most commonly associated with peanut or tree nut ingestion, and are often linked to delayed use or lack of proper epinephrine dosing 1.
- The highest risk groups for fatal anaphylaxis associated with food ingestion include adolescents and young adults, individuals with known food allergies and a prior history of anaphylaxis, and individuals with asthma, especially those with poor control 1.