Anaphylaxis: severe allergic reaction

Anaphylaxis is a severe allergic reaction that can rapidly affect breathing, circulation, skin or the digestive system.

It happens when the immune system reacts strongly to a trigger. Symptoms may involve more than one body system and can worsen quickly. Treat suspected anaphylaxis as an emergency, even if the person has had a milder reaction in the past.

Facial swelling and shortness of breath are very common presentations of anaphylaxis. Wheezing and difficulty swallowing are also common. Other warning signs include throat tightness, hoarse voice, widespread hives, sudden weakness, vomiting, dizziness or collapse.

Call emergency services immediately if anaphylaxis is suspected. If the person has been prescribed an adrenaline auto-injector, use it as instructed without delaying emergency help. Do not allow them to stand or walk; position them according to their symptoms and emergency advice.

Food, medicines and insect stings are recognised triggers. A reaction can occur after a known allergy or as the first noticeable severe reaction. The timing of food, medicines, bites, stings and activities before symptoms began helps clinicians investigate the episode.

Avoid re-exposure to a suspected trigger until it has been reviewed. Do not test a possible trigger yourself at home.

Symptoms can begin soon after contact with a trigger and may change over a short period. Skin symptoms may be obvious, but their absence does not rule out a severe reaction when breathing or circulation is affected. Emergency observation is important because symptoms can recur after initial improvement.

A previous severe reaction, a diagnosed allergy, asthma symptoms, and regular exposure to a trigger are relevant to future planning. Your clinician may ask about exact foods, medicines, insect stings, exercise and alcohol around the reaction, as more than one factor can be involved.

Clinicians diagnose anaphylaxis from the pattern and timing of symptoms, examination and details of exposure. Allergy testing may be arranged after recovery to clarify a trigger. Take photos of a rash if it is safe to do so, and record foods, medicines and events before symptoms started.

Emergency care focuses on prompt adrenaline and support for breathing and circulation. Hospital teams monitor the response and treat additional symptoms as needed. People at risk may be prescribed adrenaline auto-injectors and taught when and how to use them.

Follow-up can include an allergy referral, trigger avoidance advice and an emergency action plan. Carry prescribed emergency medicine as directed, and tell close contacts where it is kept.

Read ingredient lists, tell healthcare professionals about medicine reactions, and make travel or dining plans that account for your trigger. Check the expiry date and condition of prescribed auto-injectors. Family members, carers and colleagues can be shown your emergency plan.

Untreated anaphylaxis can lead to severe breathing problems, shock or loss of consciousness. Emergency assessment remains necessary after using an auto-injector because further treatment or observation may be needed.

After any suspected anaphylaxis episode, arrange follow-up with a clinician experienced in allergy care. They can review the trigger, prescribe appropriate emergency treatment and create a plan for home, work, school and travel.