What is it?

Anaphylaxis is a serious allergic reaction that can be life-threatening or fatal. It happens quickly and usually involves difficulty in breathing, feeling faint or lightheaded. In some cases, it can lead to a collapse.

Some people might get skin wheals (hives) and/or angioedema before they start having difficulties in breathing.

Reaction triggers

Key triggers for anaphylaxis include: 

  • food
  • drugs
  • stinging insects such as bees, wasps and hornets.

Sometimes it is difficult or impossible to find a clear trigger; as it could be caused by a combination of occurrences.

Some people have an episode when they exercise, but for others, it is when they combine certain foods or drugs with exercise.

Testing for triggers

Anyone who has had an anaphylactic reaction should have a follow-up with a specialist to help identify and avoid the trigger(s).

Something in your medical or family history, or from skin or blood tests can be enough to identify the trigger. In other cases, it may involve careful challenge (provocation) testing in hospital, under medical supervision.

If you have had a reaction, you should receive a list of the triggers involved and a plan of how to manage any future episodes.

Find out more about our asthma and allergy services

Click on the 'Information' tab to find out more about treatments for anaphylaxis and contact information. 

Skin prick testing

Skin prick testing is a universal allergy test and often used to find out what is causing an allergy. 

Oral food challenge

Oral food challenges are tests that use suspected food allergens. The foods that we most commonly test are peanuts, tree nuts and shellfish.

Drug challenge testing

This form of testing comprises of a series of tests to see if you are allergic to certain drugs, all under close medical supervision. 

Molecular diagnosis

Molecular diagnosis covers tests which can assess whether someone has antibodies against a particular protein in a food which causes an allergic reaction.

Nose clinic tests

Patients coming to the nose clinic will have a number of tests, often including an examination using an endoscope, skin prick testing, chest peak expiratory flow and spirometry.

Nasal sprays

Corticosteroid nasal sprays or drops are the most effective standard treatment for hay fever and other nasal allergies.


Antihistamines prevent histamine causing the itching and swelling that occurs when you have allergies.


Allergen immunotherapy is a treatment in which the allergen that triggers an allergic reaction is given in order to suppress unnecessary reactions.

Treatments for anaphylaxis

Self-injected adrenaline is the best treatment to give immediately when a reaction happens. You may also be prescribed other drugs such as corticosteroids and antihistamines to take.

If your reaction is caused by insect stings, you may be given specific allergen immunotherapy (‘desensitisation’). This may be necessary to protect against further allergic reactions.

The Anaphylaxis Campaign website offers further support for those living with anaphylaxis and their families.

Allergy team contact information


Fulham wing/South block, Fulham Road

Tel: 020 7351 8892
Fax: 020 73518949