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An allergy is a reaction the body has to normally harmless substances, such as pollens, foods and medicines. Usually these substances pose no problem. If you are allergic to a particular substance, your body identifies them as a ‘threat’ and reacts.

About allergies

Allergies are becoming increasingly common.

Some allergies begin in childhood and go away as a child gets older; although many are life-long.

Adults can develop allergies to things they weren't previously allergic to.

Common allergies

Having an allergy can be a nuisance, affecting your everyday activities. Most allergic reactions are mild and can be controlled. Severe reactions occasionally occur, but these are not common.

Substances that cause allergic reactions are called ‘allergens’. The more common allergens include:

  • grass and tree pollen – an allergy to these is known as hay fever (allergic rhinitis)
  • dust mites
  • animal dander (tiny flakes of skin or hair)
  • food – particularly nuts, fruit, shellfish, eggs and cow's milk
  • insect bites and stings
  • medication – including ibuprofen, aspirin, and certain antibiotics
  • latex – used to make some gloves and condoms
  • mould – these can release small particles into the air that you can breathe in
  • household chemicals – including those in detergents and hair dyes

Most of these allergens are generally harmless to people who aren't allergic to them.

Symptoms of an allergic reaction

Allergic reactions usually happen quickly within a few minutes of exposure to an allergen.

They can cause:

  • sneezing
  • a runny or blocked nose
  • red, itchy, watery eyes
  • wheezing and coughing
  • a red, itchy rash
  • worsening of asthma or eczema symptoms

Most allergic reactions are mild.  Occasionally a severe reaction called anaphylaxis or anaphylactic shock can occur. This is a medical emergency and needs urgent treatment.

Getting help for allergies

See your GP if you think you or your child might have had an allergic reaction to something.

The symptoms of an allergic reaction can also be caused by other conditions.

If your GP thinks you might have a mild allergy, they can offer advice and treatment to help manage the condition.

If your allergy is particularly severe or it's not clear what you're allergic to, your GP may refer you to an allergy specialist. This is for testing and advice about avoiding allergens, or for treatment of your symptoms.

How to manage an allergy

In many cases, the most effective way of managing an allergy is to avoid the allergen that causes the reaction whenever possible.

For example, if you have a food allergy, you should check a food's ingredients list for allergens before eating it. The Food Standards Agency has more information about food allergen labelling.

There are also several medications available to help control symptoms of allergic reactions. Your pharmacist will be able to advise you about medication to help with your symptoms.  If these do not help to control your symptoms, you should see your GP.

Causes of allergies

Allergies occur when the body's immune system reacts to a particular substance as though it's harmful.

It's not clear why this happens. Most people affected have a family history of allergies or have closely related conditions such as asthma or eczema.

Is it an allergy, sensitivity or intolerance?

Below is information to help explain the difference between an allergy, sensitivity or intolerance:

  • allergy – a reaction produced by the body's immune system when exposed to a normally harmless substance
  • sensitivity – the exaggeration of the normal effects of a substance; for example, the caffeine in a cup of coffee may cause extreme symptoms, such as palpitations and trembling
  • intolerance – where a substance causes unpleasant symptoms, such as diarrhoea, but doesn't involve the immune system; people with an intolerance to certain foods can typically eat a small amount without having any problems

Useful resources

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