Introduction 

Anaphylaxis is a severe, potentially life-threatening allergic reaction that can develop rapidly.

It is also known as anaphylactic shock.

Signs of anaphylaxis include:

  • itchy skin or a raised, red skin rash
  • swollen eyes, lips, hands and feet
  • feeling lightheaded or faint
  • swelling of the mouth, throat or tongue, which can cause breathing and swallowing difficulties
  • wheezing
  • abdominal pain, nausea and vomiting
  • collapse and unconsciousness

What to do

Anaphylaxis should always be treated as a medical emergency.

If available, an injection of a medicine called adrenaline should be given as soon as possible.

Some people with a previous history of anaphylaxis will have an auto-injector of adrenaline. This should be injected into their outer thigh muscle and held in place for 5-10 seconds. Instructions for how to use these auto-injectors can be found on the side of each device.

You should call 999 for an ambulance whether adrenaline has been given or not.

If after 5-10 minutes the person still feels unwell, a second injection should be given. This should be given in the opposite thigh.

A second dose may also be needed if the person improves and then becomes unwell again.

The person should lie flat with their legs raised on a chair or a low table. If they are having difficulty breathing, they should sit up to make breathing easier.

If the person is unconscious, you should move them in the recovery position (on their side, supported by one leg and one arm, with the head tilted back and the chin lifted). If the person's breathing or heart stops, cardiopulmonary resuscitation (CPR) should be performed.

Further treatment will be carried out in hospital.

Read more about treating anaphylaxis.

Causes and triggers

Anaphylaxis is the result of your body's immune system overreacting to a harmless substance, such as food.

Substances that trigger allergic reactions are known as allergens.

Anaphylaxis usually develops within minutes of contact with an allergen, but sometimes the reaction can happen up to four hours later.

The most widely reported triggers of anaphylaxis are:

  • insect stings – particularly wasp and bee stings
  • peanuts and tree nuts
  • other types of foods – such as milk and seafood
  • certain medicines – such as antibiotics

Read more about the causes of anaphylaxis.

Preventing further episodes

If you know what has triggered anaphylaxis, it’s important to take steps to avoid exposure to similar triggers.

You should be referred to a specialist allergy clinic to either find out your allergy triggers, or if you already know what causes it, for further assessment and advice about how to avoid allergens in the future.

You may be given two adrenaline auto-injectors to use during any future episodes of anaphylaxis.

Read more about preventing anaphylaxis

Who is affected?

Anaphylaxis is not common, but people of all ages can be affected.

People with other allergic conditions, such as asthma or the allergic skin condition atopic eczema, are most at risk of developing anaphylaxis.

Although the condition is life-threatening, deaths are rare. There are around 20 deaths in the UK each year. With prompt and proper treatment, most people make a full recovery.

 

Page last reviewed: 04/12/2014

Next review due: 04/12/2016