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What is an allergy?

An allergy is caused by your body having a bad reaction to a food or other substance that it comes into contact with. The body overreacts, as if the allergen is a harmful substance.

Allergies are more common than you might think, with 1 in 4 people in the UK believed to be affected at some point in their lives. Allergies are very common amongst children and whilst some are lifelong, some can go as a child grows up.

What are the main allergic reaction symptoms?

Allergy symptoms generally appear within a few moments of exposure to the allergen. Symptoms of a mild allergic reaction often resemble the symptoms of a cold and can include:

  • Sneezing
  • A runny nose
  • Red, watery, itchy eyes
  • A red rash
  • Wheezing or coughing

If you are prone to asthma and eczema, you may also find those symptoms worsening.

Serious allergic reactions can lead to anaphylaxis or anaphylactic shock. This requires urgent medical attention.

What causes allergies and allergic reactions?

Allergies are caused by your body having a reaction to something as if it is a harmful substance. Many people who are affected by allergies have a family history of it, or have related conditions such as asthma or eczema.

Some of the most common allergies are caused by regular, everyday things such as:

  • Pollen
  • Insect bites
  • Foods such as nuts, shellfish and cow’s milk
  • Mould
  • Certain medications (such as antibiotics or ibuprofen)
  • Dust mites
  • Animal dander

Your GP will be able to work out if it’s likely that you have an allergy to something. If it’s mild, they will be able to give you some advice as to the best way to manage it. If it’s severe, or it’s not clear what is causing your allergy, your doctor may refer you to an allergy specialist.

How can you treat an allergy?

Certain medications can help to control the symptoms of an allergic reaction. These include:

  • Antihistamines, which can be taken before exposure to an allergen to prevent a reaction and after you notice the first symptoms of an allergic reaction
  • Decongestants to help unblock a stuffy nose in the short term
  • Moisturising creams to reduce skin itching and redness
  • Steroid medications such as tablets, creams, drops, inhalers and sprays that reduce the redness and swelling caused by a reaction

People who suffer from severe allergic reactions may be treated with immunotherapy, which involves being exposed to the allergen in such a way that the body begins to get used to it and doesn’t have such bad reactions.

What can you do to prevent an allergic reaction?

The best way to prevent an allergic reaction is to avoid any known allergens. This is sometimes easier said than done, particularly if you are allergic to dust mites, pollen or pet dander.

If you are allergic to a particular food, you should check the ingredients of a food item in a supermarket or in a meal in a restaurant before you eat it.

In some cases, taking antihistamines before being exposed to the allergen can help to prevent allergic reactions occurring.


Frequently Asked Questions

What is an allergen?

An allergen is something that causes an allergic reaction. Examples include pollen, certain foods and certain medications.

How long does an allergic reaction last?

This really depends on the kind of allergic reaction you’re having. The symptoms of an allergic reaction to a particular food can go after a few hours, but an allergic reaction on the skin can take days or even weeks to fade.

Can you develop allergies?

Yes, it is possible to develop an allergy at any point in your life.

* Please note results, timeframe and individual responses to treatments may vary from person to person. If you do need medical advice you should always speak to a doctor, pharmacist or appropriate medical professional.