Introduction

An allergy is a reaction the body has to a particular food or substance.

Allergies are very common. They're thought toaffect more than one in four people in the UK at some point in their lives.

Theyare particularly common in children. Some allergies go away as a child gets older, althoughmany are lifelong. Adults can develop allergies to things they weren't previously allergic to.

Having an allergy can be a nuisance and affect your everyday activities, but most allergic reactions are mild and can be largely kept under control. Severe reactions can occasionally occur, but these are uncommon.

Common allergies

Substances that cause allergic reactions are called allergens.The more common allergensinclude:

• grass and tree pollen an allergy to theseis known as Seasonal allergic rhinitis (allergic rhinitis)
• dust mites
• animal dander (tiny flakes of skin or hair)
• food particularlynuts, fruit, shellfish, eggs and cow's milk
• insect bites and stings
• medication including ibuprofen , aspirin, and certain antibiotics
• latex used to makesome 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 theseallergensare 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 blockednose
• red, itchy, watery eyes
• wheezing and coughing
• a red, itchy rash
• worsening of asthma or eczema symptoms

Most allergic reactions are mild, but occasionally a severe reaction called anaphylaxis or anaphylactic shock can occur. This isa medical emergency and needs urgent treatment.

Your GP can help determine whether it's likely you have an allergy.

If your GP thinks you might have amild 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 GPmay refer you to an allergy specialist for testing and advice about treatment.

The Food Standards Agency has more information about food allergen labelling .

There are also several medications available tohelp control symptoms of allergic reactions, including:

• antihistamines these can be taken when you notice the symptoms of a reaction, or before being exposed to an allergen to stop a reaction occurring
• decongestants tablets, capsules, nasal sprays or liquids that can be used as a short-term treatment for a blocked nose
• lotions and creams, such as moisturising creams (emollients) these canreduce skin redness and itchiness
• steroid medication sprays, drops, creams, inhalers and tablets that can help reduce redness and swelling caused by an allergic reaction

For some people with very severe allergies, a treatment called immunotherapy may be recommended.

This involves being exposed to the allergen in a controlled way over a number of years, so your body gets used to it and doesn't react to it so severely.

The reasons for this are not understood, but one of the main theories is it's the result of living in a cleaner, germ-free environment, which reduces the number of germs our immune system has to deal with.

It's thought this maycause it to overreact when it comes into contact with harmless substances.