Quick answer. Anaphylaxis is a rapid, life-threatening allergic reaction – usually within minutes of a trigger (food, an insect sting or medication) – causing breathing difficulty or wheeze, swelling of the throat, tongue or lips, widespread hives, dizziness or collapse. Adrenaline (epinephrine) from an auto-injector is the first-line treatment – use it immediately into the outer mid-thigh; do NOT wait or rely on antihistamines. Then call 995 and say the word “anaphylaxis.” Lay the person flat with legs raised (or let them sit up if breathing is hard), and never let them stand or walk, which can cause fatal collapse. Because symptoms can return hours later, everyone must go to hospital for observation even if they recover.
In anaphylaxis, minutes matter and adrenaline is the only treatment that reverses the life-threatening features. The most common cause of a bad outcome is delaying the adrenaline – so if in doubt, give it.
Step by step
- Recognise anaphylaxis – sudden breathing difficulty, wheeze or noisy breathing; swelling of the throat, tongue or lips or a change in voice; widespread hives; dizziness, faintness or collapse; often after a known trigger.
- Lay the person flat and raise their legs. If they are struggling to breathe, let them sit up; if vomiting or drowsy, use the recovery position. Do not let them stand, walk or suddenly sit up.
- Give the adrenaline auto-injector immediately into the outer mid-thigh (see below). Don’t delay to look for antihistamines.
- Call 995 and state clearly that it is anaphylaxis.
- Note the time the adrenaline was given.
- If there is no improvement, a second dose can be given using another auto-injector into the other thigh – follow the timing in the person’s prescribed anaphylaxis action plan (commonly after about 5 minutes).
- Stay with the person and monitor breathing and consciousness. If they stop breathing normally, begin CPR.
- Go to hospital for observation even after a full recovery, because symptoms can return (a biphasic reaction).
How to use an adrenaline auto-injector (e.g. EpiPen)
- Form a fist around the auto-injector with the orange tip pointing down (“blue to the sky, orange to the thigh”).
- Pull off the blue safety cap.
- Place the orange end against the outer mid-thigh at a right angle – it can be given through light clothing (avoid seams and pockets).
- Push firmly until it clicks and hold in place for 3 seconds.
- Remove and gently massage the site for a few seconds. For a child, hold the leg firmly still during the injection.
Do and don’t
Do: give adrenaline first and fast at the first signs; inject into the outer mid-thigh (through clothing if needed); call 995 and say “anaphylaxis”; keep the person lying flat with legs raised (or sitting only if breathing is hard); give a second dose if there is no improvement, per their action plan; and go to hospital for observation even after recovery.
Don’t: delay adrenaline to try antihistamines or an inhaler first (they don’t treat anaphylaxis); let the person stand up or walk (a sudden upright posture can cause fatal collapse); put a thumb over either end of the auto-injector, or inject into a buttock, hand or foot; assume recovery is the end (biphasic reactions occur); or skip the ambulance just because the auto-injector worked.
How it differs from a mild allergy
A mild or moderate allergy stays local – an itchy rash, hives, a runny nose or a little swelling. Anaphylaxis is systemic and life-threatening: any breathing difficulty, throat or tongue swelling, dizziness or collapse means anaphylaxis, and adrenaline should be given. If someone with a known allergy develops breathing difficulty or collapse and you are unsure, give the adrenaline – it is safe, and delay is the main cause of death. See our guide to anaphylaxis and severe allergy.
Related first-aid & emergency guides
- Hands-only CPR: how to help in cardiac arrest
- How to use an AED (defibrillator)
- Choking first aid: adult, child & infant
- How to stop severe bleeding
- Burns & scalds first aid
- Seizure first aid
- The recovery position & the unconscious casualty
- Heat exhaustion & heat stroke first aid
- Head injury: when to worry
Related condition guides
- Stroke warning signs (FAST)
- Heart attack warning signs
- Anaphylaxis & severe allergy
- Epilepsy & seizures
Sources
- HealthHub (MOH, Singapore) — Adrenaline auto-injector (EpiPen and EpiPen Jr): device steps (blue safety release, orange tip, right angle to the outer thigh, hold 3 seconds), when to use, storage, and seeking emergency care after.
- ASCIA — How to give an adrenaline auto-injector / first-aid plan for anaphylaxis (ordered action steps and device technique; hold a child’s leg still).
- Allergy UK / Better Health Channel — lie flat, don’t stand or walk, adrenaline first, second dose if no improvement, biphasic reaction and hospital observation.
- Allergy & Asthma Awareness Association (AAA) Singapore — local guidance on food allergy, action plans and auto-injector prescription.