Anaphylaxis

The most severe type of allergic reaction. It can become life-threatening within minutes, but adrenaline works fast. If in doubt, give adrenaline and call an ambulance.

Quick answer: Anaphylaxis is a severe, rapid allergic reaction affecting breathing or circulation. Signs include difficult or noisy breathing, tongue or throat swelling, wheeze, a hoarse voice, dizziness or collapse, and pale, floppy young children. Lay the person flat, give an adrenaline autoinjector into the outer thigh, then call an ambulance. If in doubt, give adrenaline.

Signs of anaphylaxis

Watch for any one of these (ASCIA):

• Difficult or noisy breathing
• Swelling of the tongue
• Swelling or tightness in the throat
• Wheeze or a persistent cough
• Difficulty talking or a hoarse voice
• Persistent dizziness or collapse
• Pale and floppy (young children)
• For insect sting allergy, tummy pain and vomiting are also signs of anaphylaxis

Milder allergic reactions cause swelling of the lips, face or eyes, hives or welts, or a tingling mouth. Mild signs don’t always come before anaphylaxis, so watch closely and have adrenaline ready.

What to do: ASCIA first aid

1. Lay the person flat. Don’t let them stand or walk. If they’re unconscious or pregnant, place them on their side (left side if pregnant). If breathing is hard, let them sit with legs out straight. Hold young children flat, not upright.
2. Give an adrenaline autoinjector into the outer mid-thigh.
3. Call an ambulance: 000 in Australia, 111 in New Zealand, or your local emergency number.
4. Phone family or an emergency contact.
5. Give another dose of adrenaline if there’s no response after 5 minutes, if a second device is available.
6. Go to hospital for at least 4 hours of observation, even if they feel better.

If in doubt, give adrenaline. Start CPR at any time if the person is unresponsive and not breathing normally. If someone with asthma and a known allergy has sudden trouble breathing, give adrenaline first, then their asthma reliever puffer.

How to use an adrenaline autoinjector

Devices differ slightly. Learn yours from its label and your action plan, and practise with a trainer device.

1. Take the device out of its case and hold it in your fist, without touching either end.
2. Pull off the safety cap or release (and the needle shield, on some devices).
3. Place the tip against the outer mid-thigh. It works through clothing.
4. Push down hard until it clicks (or press the button, on some devices), and hold it in place for 3 seconds.
5. Remove it, note the time, and give the used device to the ambulance crew.

Your doctor chooses the dose by body weight. Check the expiry date regularly and store devices at room temperature, out of direct sun. If adrenaline is accidentally injected into a finger or hand, call the Poisons Information Centre (13 11 26 in Australia) and keep following the action plan. An adrenaline nasal spray is approved in some countries as another option.

Common triggers

• Foods: peanut, tree nuts, egg, cow’s milk, sesame, fish, shellfish, soy and wheat. Food is the most common cause in children.
• Insect stings: bees and wasps, and in Australia, jack jumper and other ants. See insect bites and stings.
• Medicines: such as some antibiotics (including penicillins), anti-inflammatory painkillers and medicines used during anaesthesia. Medicines and insect stings are common causes in adults.
• Ticks: in Australia, tick bites can cause anaphylaxis and a delayed allergy to red meat (mammalian meat allergy). Freeze ticks off rather than pulling them out.
• Others: latex, exercise (sometimes only after a particular food), and sometimes no cause is found.

After anaphylaxis

• Antihistamines don’t treat anaphylaxis. They only ease itching and hives. Adrenaline is the treatment.
• Some people have a second wave of symptoms hours later, which is why hospital observation matters.
• See an allergy specialist (clinical immunology and allergy) to confirm the trigger and plan treatment.
• Carry your adrenaline autoinjector at all times, with your action plan. In Australia they’re PBS-subsidised with a prescription.
• Venom immunotherapy (desensitisation) greatly reduces the risk of another severe reaction to insect stings.
• Wear medical identification, and tell schools, childcare and workplaces.

Action plans

ASCIA action plans tell others exactly what to do. The red ASCIA Action Plan for Anaphylaxis is for people prescribed adrenaline; the green plan is for people with allergies who haven’t been prescribed adrenaline; the orange general first aid plan is for schools, workplaces and first aid kits. Your doctor completes and signs your plan. Update it when you get a new device or every time your child’s weight changes a lot.

Save your money

Popular, heavily marketed or often asked about, but the evidence is weak or says no.

• IgG food tests, hair analysis and kinesiologyASCIA warns these unproven tests don’t diagnose allergies and can lead to unnecessary food avoidance. Allergy testing should be done by a doctor.

See your GP if

• You’ve had a reaction with swelling, hives or breathing symptoms after a food, sting or medicine
• You’ve been treated for anaphylaxis: you need a follow-up, an action plan and a specialist referral
• Your adrenaline device is expiring or has been used
• Your child has a food allergy and is starting school or childcare

Call 000 (Australia) or your local emergency number straight after giving adrenaline, or straight away if you don’t have it. Don’t drive yourself to hospital.

Evidence and more information

• ASCIA Action Plan for Anaphylaxis (2025)
• ASCIA First Aid Plan for Anaphylaxis (general, 2023)
• healthdirect: How to use an adrenaline autoinjector
• Cardona et al, World Allergy Organization anaphylaxis guidance 2020
• Resuscitation Council UK 2021: Emergency treatment of anaphylaxis
• NICE CG134: Anaphylaxis, assessment and referral after emergency treatment

Updated 8 November 2026. General education, not personal medical advice. Follow your own signed ASCIA action plan and your doctor’s advice.

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