Anaphylaxis is a severe and potentially life-threatening reaction to a trigger such as an allergy.
Anaphylaxis usually develops suddenly and gets worse very quickly.
The symptoms include:
There may also be other allergy symptoms, including an itchy, raised rash (hives); feeling or being sick; swelling (angioedema) or stomach pain.
Anaphylaxis is a medical emergency. It can be very serious if not treated quickly.
If someone has symptoms of anaphylaxis, you should:
- Use an adrenaline auto-injector if the person has one – but make sure you know how to use it correctly first.
- Call 999 for an ambulance immediately (even if they start to feel better) – mention that you think the person has anaphylaxis.
- Remove any trigger if possible – for example, carefully remove any stinger stuck in the skin.
- Lie the person down flat – unless they're unconscious, pregnant or having breathing difficulties.
- Give another injection after 5 to 15 minutes if the symptoms do not improve and a second auto-injector is available.
If you're having an anaphylactic reaction, you can follow these steps yourself if you feel able to.
Read about how to treat anaphylaxis for more advice about using auto-injectors and correct positioning.
Anaphylaxis is the result of the immune system, the body's natural defence system, overreacting to a trigger.
This is often something you're allergic to, but not always.
Common anaphylaxis triggers include:
In some cases, there's no obvious trigger. This is known as idiopathic anaphylaxis.
If you have a serious allergy or have experienced anaphylaxis before, it's important to try to prevent future episodes.
The following can help reduce your risk:
- identify any triggers – you may be referred to an allergy clinic for allergy tests to check for anything that could trigger anaphylaxis
- avoid triggers whenever possible – for example, you should be careful when food shopping or eating out if you have a food allergy
- carry your adrenaline auto-injector at all times (if you have 2, carry them both) – give yourself an injection whenever you think you may be experiencing anaphylaxis, even if you're not completely sure
Read more about preventing anaphylaxis
Page last reviewed: Tue Nov 2022
Next review due: Tue Nov 2022