This NHS content is written for people in England. Services, entitlements and contact routes may differ in other countries.
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
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.
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.
Allergies
Allergies
Allergies
Allergies
Symptoms of a mild allergic reaction include sneezing, a runny nose, itchy skin and a raised rash (hives).
Common types of allergies include allergies to pollen, house dust mites, food (such as peanuts, milk and eggs) and animals.
Tests to diagnose an allergy may include a skin prick test, blood tests, a patch test or going on a special diet to see if your symptoms improve.
Treatment for allergies includes avoiding the thing you're allergic to whenever possible and medicines like antihistamines to reduce the symptoms.
Content supplied by the NHS website, refreshed 19 August 2026. View the original NHS article ↗
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