Causes of anaphylaxis

The three most common agents leading to severe anaphylaxis are certain foods, insect stings and medications. Common triggers include:

Food
Eggs, nuts and seafood are the most common food triggers; however, any food can trigger anaphylaxis. Even trace amounts of food can cause a life-threatening reaction. Some extremely sensitive individuals can react to even the smell of a food (e.g., fish).

Insect Venom
Bee, wasp and jumper ant stings are the most common causes of anaphylaxis to insect stings. Ticks and fire ants also cause anaphylaxis in susceptible individuals.

Medication
Medications (e.g. penicillin), both over the counter and prescribed, can cause life threatening allergic reactions. Individuals can also have anaphylactic reactions to herbal or ‘alternative’ medicines.

Other
Other triggers such as latex or exercise induced anaphylaxis are less common and occasionally the trigger cannot be identified despite extensive investigation.

Food-Dependent Exercise-Induced Anaphylaxis
Food-dependent, exercise-induced anaphylaxis is very rare and occurs only when an individual eats a specific food and exercises within 3-4 hours after eating this food. Although any food may contribute to this form of anaphylaxis, foods that have been reported include wheat, shellfish, fruit, milk, celery, and fish.

Idiopathic Anaphylaxis
Idiopathic anaphylaxis is anaphylaxis in which no cause can be determined. This reaction may occur at night or after foods that have been eaten many times previously. Idiopathic anaphylaxis can be frequent (if there are 6 or more episodes per year or two episodes in the last 2 months) or infrequent (if episodes occur less often).