Allergies
Key facts
Allergies occur when your immune system overreacts to a normally harmless substance (allergen). Hay fever, which the NHS describes as a common allergy, is one of the most familiar. Symptoms range from mild sneezing to life-threatening anaphylaxis.
Most often affects:Children and young adultsPeople with eczema or asthmaThose with family history of allergies
What commonly causes allergies
- Pollen — grass, tree, or weed pollen (hay fever / allergic rhinitis)
- Dust mites — found in mattresses, pillows, and carpets
- Pet dander — proteins from cat and dog skin, saliva, and urine
- Mould spores — in damp areas of the home
- Certain foods — nuts, shellfish, dairy, eggs, wheat
- Insect stings — bees, wasps
- Certain medicines — antibiotics such as penicillin, ibuprofen and aspirin are common triggers
What helps at home
- Antihistamines do not treat a severe allergic reaction (anaphylaxis). If you have been prescribed an adrenaline auto-injector, carry two at all times, use one at the first sign of throat, lip or tongue swelling or breathing difficulty, call 999, and lie down with your legs raised — do not stand or walk even if you feel better.
- Take non-drowsy antihistamines (cetirizine or loratadine) daily during allergy season
- Keep windows closed on high pollen days (check the pollen forecast)
- Shower and change clothes after being outdoors
- Use a nasal saline spray or rinse to clear allergens
- Vacuum regularly with a HEPA filter and wash bedding weekly at 60°C
- Apply petroleum jelly around nostrils to trap pollen
When to get help
These three levels are different. Getting the level right is the single most useful thing this page can do for you.
Non-urgent advice: see a GP if
- Symptoms have not improved with over-the-counter antihistamines
- Allergies are significantly affecting your sleep, work or quality of life
- You want allergy testing to identify your triggers
- Symptoms are year-round and you want to discuss immunotherapy
Urgent advice: ask for an urgent GP appointment or call 111 if
- Widespread hives came on quickly after a food, sting or medicine
- Widespread hives with no swelling of the lips, mouth, throat or tongue and no difficulty breathing
- You have taken an antihistamine and the reaction is still spreading
Immediate action required: call 999 or go to A&E if
- Difficulty breathing, wheezing, or throat tightening
- Swelling of lips, tongue, face, or throat
- Wheeze, chest or throat tightness, or difficulty swallowing after contact with an allergen
- Sudden confusion, drowsiness or dizziness after contact with an allergen — lie down, do not stand or walk, even if you feel better
- Feeling faint, dizzy, or collapsing — signs of anaphylaxis
- If prescribed: use your adrenaline auto-injector (EpiPen) immediately, then call 999
What to do next
Not sure whether allergies needs a doctor? These are your options, cheapest and fastest first.
Questions people ask about allergies
Reducing the chance of it coming back
- Know your triggers — get tested if unsure
- Speak to a pharmacist before pollen season about which antihistamine or steroid nasal spray suits you, and when to start taking it.
- Consider allergen-proof mattress and pillow covers
- Keep pets out of bedrooms if allergic to dander
Conditions this can be part of
Listed alphabetically, not by likelihood — this page does not tell you which one you have.
- Allergic rhinitis
- Anaphylaxis
- Asthma
- Hay fever
Sources and further reading
This page was written from the following published guidance. All links checked 26 August 2026.
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