From the Guidelines
Yes, someone can experience anaphylaxis after 2 hours of eating an offending agent, as food-induced anaphylaxis can have a rapid onset and evolution of symptoms over minutes to several hours. According to the guidelines for the diagnosis and management of food allergy in the United States, reported by the NIAID-sponsored expert panel 1, deaths from food-induced anaphylaxis have been reported within 30 minutes to 2 hours of exposure. The time course of an anaphylactic reaction may be uniphasic, biphasic, or protracted, with biphasic reactions typically occurring about 8 hours after the first reaction, although recurrences have been reported up to 72 hours later.
Key points to consider:
- Fatalities associated with food-induced anaphylaxis are most commonly associated with peanut or tree nut ingestion 1
- The highest risk groups for fatal anaphylaxis associated with food ingestion are adolescents and young adults, individuals with known food allergy and a prior history of anaphylaxis, and individuals with asthma, especially those with poor control 1
- Anyone experiencing symptoms of anaphylaxis should use an epinephrine auto-injector immediately and call emergency services, as delayed reactions can be life-threatening
- After using epinephrine, the person should be transported to an emergency room for observation, as some patients require a second dose and monitoring 1
It is essential to note that people with known severe allergies should always carry epinephrine auto-injectors and wear medical alert identification, as anaphylaxis can occur at any time after exposure to the offending agent.
From the Research
Anaphylaxis Onset
- Anaphylaxis is a life-threatening systemic reaction that normally occurs within one to two hours of exposure to an allergen 2.
- The "rule of 2's" for anaphylaxis implies that reactions usually begin within 2 minutes to 2 hours after injection, infusion, ingestion, contact, or inhalation 3.
- This suggests that it is possible for someone to have anaphylaxis after 2 hours of eating the offending agent, although it is less common.
Anaphylaxis Symptoms and Treatment
- Symptoms of anaphylaxis can include urticaria, difficulty breathing, and mucosal swelling 2.
- Treatment of anaphylaxis involves removal of the trigger, early administration of intramuscular epinephrine, and supportive care for the patient's airway, breathing, and circulation 2.
- Patients should be monitored for a biphasic reaction, which can occur within 4 to 12 hours after the initial reaction 2.
Biphasic Reactions
- Biphasic reactions are a recurrence of anaphylaxis without reexposure to the allergen 2.
- The risk of biphasic reactions is a consideration in determining the length of observation after an anaphylactic reaction 4.
- However, biphasic reactions are difficult to predict and may occur outside of typical observation periods 4.