How do I recognise anaphylaxis and what do I do?
The signs that separate a severe reaction from a mild one, the immediate actions in order, the position that matters, and why a second auto-injector exists.
- Difficulty
- beginner
- Time
- 7 min
- Read
- 4 min
- Safety
- warning
Short answer
Airway, breathing or circulation involvement is what makes it anaphylaxis: swelling of the throat or tongue, difficulty breathing or noisy breathing, a hoarse voice, feeling faint or collapsing, pale or blue skin. Ring 999. Use an adrenaline auto-injector into the outer thigh if there is one. Keep them lying down with legs raised, or sitting up if breathing is the problem. If there is no improvement after 5 minutes, use a second injector.
Mild allergic reactions are common and anaphylaxis is not, and the difference is not about how uncomfortable it looks. It is about whether the airway, the breathing or the circulation is involved. That distinction is what this page is for, and getting it right early is what makes the difference.
Safety
Step by step
- Look for airway involvement.Swelling of the throat or tongue, difficulty swallowing, a tight throat, a hoarse voice or a change in the sound of the voice. Any of these is anaphylaxis until proved otherwise.
- Look for breathing involvement.Difficulty breathing, breathing very fast, wheezing, coughing or noisy breathing. In someone with asthma, a sudden severe attack after an exposure should be treated as anaphylaxis.
- Look for circulation involvement.Feeling faint, dizziness, collapse, confusion or tiredness, skin that feels cold, and skin, lips or tongue that look blue, grey or pale.
- Ring 999 straight away.Say you think it is anaphylaxis. That word changes the response. Do this even if an auto-injector has already been used and the person seems to be improving.
- Use the adrenaline auto-injector.Into the outer mid-thigh, through clothing if necessary, following the instructions on the device itself — the devices differ and each is labelled. Note the time you gave it.
- Get the position right.NHS advice is to lie down, with the legs raised if possible. If breathing is difficult, raise the shoulders or sit up slowly. In pregnancy, lie on the left side. If they are unresponsive but breathing, use the recovery position.
- Do not let them stand or walk.This is emphasised in the guidance for a reason: standing or sitting up suddenly during or after anaphylaxis can cause a fatal drop in blood pressure. Even if they say they feel fine, they stay down until the ambulance crew says otherwise.
- Remove the trigger if it is still there.Scrape or brush an insect sting off the skin rather than pinching it. Stop any drug being given. Do not make them vomit food.
- Give a second injector after five minutes if there is no improvement.NHS guidance is a second adrenaline auto-injector after five minutes if the person is not improving. This is why people at risk are prescribed two.
- Keep watching even if they improve.Symptoms can return after an apparent recovery, which is why hospital assessment is required after any anaphylaxis, whatever the improvement looks like.
Tips
- If someone carries auto-injectors, find out now where they keep them and how their device works. In the moment is a bad time to read a leaflet.
- Auto-injectors have expiry dates and people carry expired ones without realising. An expired injector is better than none, but replacing it is a two-minute job on a repeat prescription.
- Ambulance control will stay on the line. Say what you have given and at what time.
Common mistakes
- Waiting to see whether it settles before using adrenaline — Adrenaline works best given early, and the risk of giving it unnecessarily is very low compared with the risk of delay. Hesitation is the recurring theme in serious outcomes.
- Using an antihistamine instead — Antihistamines treat the skin symptoms of a mild reaction. They do nothing for airway swelling or a falling blood pressure, and reaching for one instead of adrenaline wastes the minutes that matter.
- Letting the person walk to the car or to the door — Standing up can cause a sudden fatal fall in blood pressure. They stay lying down and the ambulance comes to them.
- Not going to hospital because the injector worked — Symptoms can return hours later. Hospital assessment after anaphylaxis is standard and it is not a formality.
If it doesn't work
The reaction is a rash and itching only, with no breathing or throat involvement
Cause: A mild or moderate allergic reaction — Fix: That is not anaphylaxis. Follow NHS advice for a mild reaction and watch closely for any airway, breathing or circulation symptom developing — a mild reaction can progress.
You are not sure whether it is anaphylaxis
Cause: Symptoms that are developing and unclear — Fix: Ring 999 and describe what you see. Uncertainty is a reason to call, not a reason to wait, and the handler will tell you whether to use the injector.
They become unresponsive
Cause: Anaphylaxis progressing — Fix: Check breathing. Breathing normally means recovery position; not breathing normally means chest compressions and CPR. Tell the 999 handler what has changed.
Questions people ask
What if I use the injector and it turns out not to be anaphylaxis?
Adrenaline given to someone who did not need it is very unlikely to do serious harm to an otherwise healthy person. Adrenaline withheld from someone who did need it can be fatal. The guidance is deliberately weighted towards giving it.
Where exactly does the injector go?
Into the outer mid-thigh muscle, and it works through clothing. Every device is labelled with its own instructions, and they differ between brands — read the one you are holding.
How quickly does anaphylaxis develop?
Usually within minutes of exposure, though it can be slower. A reaction that is getting worse rather than settling is the pattern to act on.
Can it happen with no known allergy?
Yes. A first anaphylactic reaction, by definition, happens to someone who did not know they were allergic. The absence of a known allergy is not a reason to doubt what you are seeing.