What causes anaphylaxis?

In anaphylaxis, the immune system releases chemical messengers throughout the body after exposure to a trigger. These chemicals can widen blood vessels, lower blood pressure, tighten the airways and cause tissue swelling. The resulting pattern may include hives, facial or tongue swelling, vomiting, wheezing, throat tightness, dizziness or collapse.

A trigger may be obvious from the timing, but sometimes it remains uncertain. Foods, prescribed or over-the-counter medicines, insect stings and latex are recognised triggers. Exercise can contribute in some people, occasionally together with another factor such as eating a particular food. A previous mild reaction does not reliably predict how a later exposure will unfold.

Stop exposure when this is immediately possible, but prioritise treatment. Use prescribed epinephrine at once when anaphylaxis is suspected and call local emergency services. Position the person safely: usually lying flat with raised legs, or seated with legs extended if breathing is difficult. Follow the individual action plan for a further dose if symptoms persist or recur.

Keep any food packaging, medicine name or details about an insect exposure for the later clinical history, provided collecting them does not slow emergency care. Do not deliberately test a suspected trigger at home.

Emergency help is required for throat or tongue swelling, breathing difficulty, a hoarse voice, persistent wheezing, fainting, confusion, collapse, or rapidly progressing symptoms in different body systems. Anyone treated with epinephrine needs urgent medical assessment even after improvement, because the reaction can return.

Bring a timeline of foods, medicines, exercise, bites or stings and symptom onset to the appointment. Ask whether referral to an allergy specialist and targeted testing are suitable. Also confirm what to avoid while the cause is being assessed, which substitute medicines or foods are appropriate, and when to use your auto-injector.