Lots of us suffer from allergies - be it pets, nuts, pollen or something else. Find out what an allergy actually is here, and ways to detect if you have one...

The body mistakes an otherwise harmless substance for something dangerous

What is an allergy?

An allergy is a bad physical reaction to something we've come into contact with - known in the trade as an allergen. It is often harmless to other people, and people can be allergic to all kinds of substances. The most common allergens are pollen, nuts, pets and dust. Each time we come into contact with our allergen, we get the same reaction shortly afterwards.

About 25% of us have an allergy, and for most of us this is simply annoying - we just have to avoid certain things. But for some, the reaction is extreme - in these cases some people even carry medicine to use in an emergency.

Why do we get an allergy?

No one knows for sure. But we haven't caught it from someone or caused it to happen - the body simply mistakes an otherwise harmless substance for something dangerous, and triggers a response. We're more likely to have allergies if people in our family do, or if we have eczema, hay fever or asthma.

How do I know if I have an allergy?

Our immune system spots the allergen, freaks out and makes an excessive response even though the substance is otherwise harmless. It's like throwing a huge tantrum over nothing.

This affects different people different ways, but common reactions include:

  • Itchy, watery eyes
  • Runny, sneezy nose
  • Coughing
  • Wheeze (a high pitched sound when we breathe out)
  • Rashes (most commonly blotches or little red bumps)
  • Vomiting and/or diarrhoea

If you're worried about allergies, see your GP.

How will the doctor know if I am allergic?

The doctor will ask questions, as they need to know as much as possible about the reaction and our health in general. Then we may get an allergy test - either a blood or skin tests, which will reveal what we're allergic to. We then get advice about how to deal with it, and possibly treatment.

When I eat white bread I get tummy ache. Am I allergic?

It's more likely to be a food intolerance - intolerances to things like gluten or lactose (found in dairy) are very common. The symptoms are usually less predictable and less severe than for true allergy. If in doubt, see your doctor.

BBC Advice factfiles are here to help young people with a broad range of issues. They're based on advice from medical professionals, government bodies, charities and other relevant groups. Follow the links for more advice from these organisations.


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