Anaphylaxis

Anaphylaxis is a severe and potentially life-threatening reaction to a trigger such as an allergy.

Symptoms of anaphylaxis

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.

What to do if someone has anaphylaxis

Anaphylaxis is a medical emergency. It can be very serious if not treated quickly.

If someone has symptoms of anaphylaxis:

  1. Use an adrenaline auto-injector if the person has one – but make sure you know how to use it correctly first.
  2. Call 999 for an ambulance immediately (even if they start to feel better) – mention that you think the person has anaphylaxis.
  3. Remove any trigger if possible – for example, carefully remove any stinger stuck in the skin.
  4. Lie the person down and raise their legs – unless they're having breathing difficulties and need to sit up to help them breathe. If they're pregnant, lie them down on their left side.
  5. Give another injection after 5 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.

Triggers of anaphylaxis

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.

Preventing 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:

Read more about preventing anaphylaxis

Page last reviewed: 29 November 2019
Next review due: 29 November 2022