Heat-induced anaphylaxis: what to know

A reaction may begin with flushing, itching, hives or swelling and progress to throat tightness, wheezing, hoarse voice, difficulty breathing, dizziness, vomiting or collapse. Heat may act alongside exercise, food or another trigger rather than being the only cause. Symptoms can worsen quickly, and a person may not develop every sign. A previous mild reaction does not predict the severity of a later episode.

Use an adrenaline auto-injector immediately if one has been prescribed for the person, following its instructions, and call emergency services. Keep the person lying down with legs raised unless breathing is easier sitting; do not let them stand or walk. A second injector may be needed if symptoms continue and emergency help has not arrived, according to the prescribed plan. Do not rely on antihistamines for breathing or circulation problems.

Treat breathing difficulty, throat or tongue swelling, faintness, wheezing or collapse as an emergency, even if a rash is absent. After recovery, arrange specialist assessment to review triggers, carry an action plan and consider allergy testing. Read more about Anaphylaxis Emergency Treatment and Anaphylaxis.

Ask whether heat, exercise, food or medicines could be interacting triggers, when to use an injector, whether you need two devices, and how family or colleagues should respond.