Reviewed by Dr. Alam Rafeul Alam, MD, PhD

An anaphylactic reaction is often triggered by an allergen exposure. An exposure may occur through injection, swallowing, inhaling or skin contact.

  • Injected Allergens: Include bee, hornet, wasp and yellow jacket stings, and allergen extracts used for diagnosis and treatment of allergic conditions. Antibiotics such as penicillin can trigger a reaction by injection or ingestion (swallowing).

  • Ingested Allergens: A severe reaction caused by a food allergy occurs after eating that particular food, even a small bite. Foods that most commonly cause anaphylaxis are peanuts, seafood, nuts and, in children, eggs and cow's milk. Skin contact with the food rarely causes anaphylaxis.

  • Inhaled Allergens: An anaphylactic reaction from an inhaled allergen is rare. An example is a latex-allergic person who inhales particles from rubber gloves or other latex products.

  • Multiple Factors: For some people, two or more factors may be needed to cause anaphylaxis. It has been recognized that an anaphylactic reaction can occur if a person eats a certain food and then exercises. Neither the food alone nor exercise alone causes any problem, but the two together do.

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