Food anaphylaxis: recognising and treating a severe food allergy reaction

Anaphylaxis is a serious whole-body allergic reaction. Anaphylaxis UK explains that the immune system wrongly identifies a food or substance as a threat, and on re-exposure antibodies called IgE trigger a sudden release of chemicals including histamine. Sometimes even tiny amounts of the allergen are enough.

The NHS lists foods that can cause it: nuts, cows' milk, eggs, fish and shellfish, and sesame seeds; other triggers include medicines, insect stings, anaesthetics and latex. This page focuses on food, and some reactions happen with no known cause.

The NHS says symptoms usually start within minutes of contact with the allergen. Signs of a reaction involving the airway, breathing or circulation include the following.

• Swelling of the lips, mouth, throat or tongue.

• Difficulty breathing, wheezing, noisy breathing, or breathing very fast.

• A tight throat, hoarse voice or difficulty swallowing.

• Feeling faint, dizzy, confused or drowsy, or fainting.

• Cold skin, or skin, lips or tongue turning blue, grey or pale.

• A swollen, raised, itchy rash.

• In a child: being limp, floppy or not responding as normal.

The NHS gives a clear sequence. Use an adrenaline auto-injector if you have one, call 999 and say you think it is anaphylaxis, and lie down with your legs raised, or sit up slowly if struggling to breathe, or lie on the left side if pregnant. If symptoms have not improved after 5 minutes, use a second auto-injector. Do not stand or walk at any time, even if you feel better.

The NHS adds that a nasal spray form of adrenaline is also available for food allergy and should be used immediately when someone is having a serious reaction, and that you must call 999 after using either device, even if you feel better. It also advises using adrenaline if you think you may have anaphylaxis even when symptoms seem mild. Do not drive yourself to A&E.

Anaphylaxis needs to be treated in hospital immediately. Treatments can include adrenaline by injection or drip, oxygen and fluids through a vein. The NHS says people usually stay for around 2 to 12 hours and sometimes longer. Before leaving, you should be given 2 adrenaline auto-injectors, or a prescription for them, and be shown how to use them. You may be referred to an allergy specialist for tests and advice.

The NHS says a GP may refer you to a specialist for tests if a food allergy is suspected. Tests may include a skin-prick test, blood tests, or a supervised diet avoiding the suspect food to see whether symptoms improve. A food and symptom diary helps. Specialists then provide an allergy action plan explaining how to manage the allergy.

The NHS notes that children with a peanut allergy may be offered immunotherapy to help their bodies become less sensitive to peanuts, but they still need to avoid eating peanuts.

NHS advice for reducing risk and being prepared includes the following.

• Avoid the food, and check labels and restaurant menus carefully; tell staff about your allergy.

• Carry 2 adrenaline auto-injectors at all times and check expiry dates regularly.

• Practise with a trainer injector and teach friends, family and colleagues when and how to use yours.

• Keep injectors away from heat and cold, such as the fridge or direct sun.

• Consider medical alert jewellery.

Anaphylaxis itself is an emergency pathway through 999 and A&E. Afterwards, NHS allergy clinics assess patients, though access varies. Private allergy clinics offer testing and consultations, but interpretation is key: positive tests do not always mean clinical allergy, so tests should be requested and read by a clinician who takes the history into account.