Emergency

Anaphylaxis (Severe Allergic Reaction)

For a severe allergic reaction, use an adrenaline auto-injector (such as an EpiPen) into the outer thigh straight away and call 999.

When to call 999. Call 999 immediately for any severe allergic reaction — signs include swelling of the lips, tongue or throat, difficulty breathing, wheeze, feeling faint, or a widespread rash with collapse. Say clearly that you suspect anaphylaxis.

Written by Meds Global Health Clinical Team · Clinically reviewed by Dr Muhammad Suffyan, MB BS, Founder & Clinical Director · Last reviewed · How we review

What to do

  1. If the person has an adrenaline auto-injector (such as an EpiPen or Jext), help them use it straight away — or use it for them — into the outer thigh, through clothing if needed.
  2. Call 999 immediately and say you suspect anaphylaxis.
  3. Help the person into a comfortable position: lie them down with legs raised if they feel faint, or sit them up if they are struggling to breathe. Do not stand them up.
  4. If there is no improvement after 5 minutes and a second auto-injector is available, use it.
  5. If they become unresponsive and stop breathing normally, start CPR.
  6. Note the time the auto-injector was used to tell the ambulance crew.

Avoid

What not to do

Do not let the person stand up or walk around, as this can cause a dangerous drop in blood pressure. Do not delay adrenaline while waiting to see if symptoms settle — give it early. Do not assume antihistamines or an inhaler alone are enough.

Afterwards and while you wait

Everyone who has had anaphylaxis needs to go to hospital, even if they seem to recover, because symptoms can return. Keep the used auto-injector to show the crew. Afterwards, they should see a doctor about allergy testing and carrying auto-injectors.

Education and reference only. This is general first-aid information aligned with UK guidance, not a substitute for a hands-on first-aid course or professional emergency care. In a life-threatening emergency, call 999 straight away.

Answers

Anaphylaxis (Severe Allergic Reaction): frequently asked questions

Can adrenaline harm someone if it turns out not to be anaphylaxis?

Adrenaline auto-injectors are designed to be safe to use, and the risk of not treating true anaphylaxis is far greater. If in doubt with severe allergic symptoms, use the injector and call 999.

Why must they go to hospital if they feel better?

Anaphylaxis can come back hours after the first reaction, so monitoring in hospital is essential even after adrenaline appears to work.

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Sources

Where this is drawn from

  • NHS — first aid
  • Resuscitation Council UK
  • St John Ambulance / British Red Cross first-aid guidance

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