Skip to main content

Allergies

An allergy is where your body reacts to something that's normally harmless like food, pollen, dust, insect bites or animals. The symptoms can be mild, but for some people they can be very serious.

Causes of allergies

Things that cause allergic reactions are called allergens.

Common allergens include:

  • tree and grass pollen (hay fever)
  • house dust mites
  • foods, such as peanuts, milk and eggs (food allergy)
  • animals, particularly pets like cats and dogs
  • insect stings, such as bee and wasp stings
  • certain medicines

Symptoms of an allergic reaction

Symptoms of an allergic reaction can appear within minutes or after a few hours.

Symptoms may include:

  • a runny nose or sneezing
  • red or watering eyes
  • pain or tenderness around your cheeks, eyes or forehead
  • coughing, wheezing or breathlessness
  • a raised rash (hives), or itchy or red skin – redness can be harder to see on brown or black skin
  • diarrhoea, stomach cramps or bloating
  • feeling or being sick
  • swollen eyes, lips, mouth or throat

Immediate action required: Call 999 if:

  • your lips, mouth, throat or tongue suddenly become swollen
  • you're breathing very fast or struggling to breathe (you may become very wheezy or feel like you're choking or gasping for air)
  • your throat feels tight or you're struggling to swallow
  • your skin, tongue or lips turn blue, grey or pale (if you have black or brown skin, this may be easier to see on the palms of your hands or soles of your feet)
  • you suddenly become very confused, drowsy or dizzy
  • someone faints and cannot be woken up
  • a child is limp, floppy or not responding like they normally do (their head may fall to the side, backwards or forwards, or they may find it difficult to lift their head or focus on your face)

You or the person who's unwell may also have a rash that's swollen, raised or itchy.

These can be signs of a serious allergic reaction (anaphylaxis). Anaphylaxis needs immediate treatment in hospital.

What to do if you have anaphylaxis

Follow these steps if you think you or someone you're with is having an anaphylactic reaction:

  1. Use an adrenaline auto-injector (such as an EpiPen) if you have one – instructions are included on the side of the injector.
  2. Call 999 for an ambulance and say that you think you're having an anaphylactic reaction.
  3. Lie down – you can raise your legs, and if you're struggling to breathe, raise your shoulders or sit up slowly (if you're pregnant, lie on your left side).
  4. If you have been stung by an insect, try to remove the sting if it's still in the skin.
  5. If your symptoms have not improved after 5 minutes, use a 2nd adrenaline auto-injector.

Do not stand or walk at any time, even if you feel better.

Information:

How to use an adrenaline auto-injector

There are different types of adrenaline auto-injectors and each one is given differently.

Non-urgent advice: See a GP if:

  • you think you or your child may have an allergy

What happens at your appointment

A GP may arrange some allergy tests or refer you to a specialist allergy clinic to have them.

Tests you may have include:

  • a skin prick test – where a small amount of the allergen is put on your skin to see if it reacts
  • blood tests
  • a special diet where you are gradually given increasing amounts of a food you might be allergic to, to see if you react

Treatments for allergies

There are different ways to manage and treat allergies, depending on the type of allergic reaction. More severe allergic reactions, such as anaphylaxis, need to be treated in hospital.

Treatments for allergies may include:

  • trying to avoid the thing you're allergic to whenever possible
  • medicines for allergic reactions, like antihistamines and steroid nasal sprays, tablets and creams
  • emergency medicines called adrenaline auto-injectors, such as an EpiPen, for severe allergic reactions
  • desensitisation (immunotherapy) – this involves carefully exposing you to the thing you're allergic to over time, so your body gradually gets used to it and does not react so badly (this should only be done by a medical professional)

If you see a specialist, they may give you an allergy management plan that will explain how to manage your allergy.

Information:

Find out more

Allergy UK: living with an allergy

Page last reviewed: 05 March 2026
Next review due: 05 March 2029