An allergy is a reaction the body has to a particular food or substance.
Half of all children in the UK have allergies. For both children and parents it is a learning curve in understanding what to avoid and how to control and manage the allergy.
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.
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 cows' milk
- insect bites and stings
- medicines – 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 are not allergic to them.
Most allergic reactions are mild, but occasionally a severe reaction called anaphylaxis or anaphylactic shock can occur.
This is a medical emergency and needs urgent treatment.
Common symptoms of an allergic reaction include:
- sneezing and an itchy, runny or blocked nose (allergic rhinitis)
- itchy, red, watering eyes (conjunctivitis)
- wheezing, chest tightness, shortness of breath and a cough
- a raised, itchy, red rash (hives)
- swollen lips, tongue, eyes or face
- tummy pain, feeling sick, vomiting or diarrhoea
- dry, red and cracked skin
The symptoms vary depending on what you're allergic to and how you come into contact with it.
For example, you may have a runny nose if exposed to pollen, develop a rash if you have a skin allergy, or feel sick if you eat something you're allergic to.
See your GP if you or your child might have had an allergic reaction to something. They can help determine whether the symptoms are caused by an allergy or another condition.
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.
There are also several medicines available to help 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 can reduce skin redness and itchiness
- steroid medicines – sprays, drops, creams, inhalers and tablets that can help reduce redness and swelling caused by an allergic reaction
The best way to prevent an allergic reaction is to avoid the substance that you're allergic to, although this is not always easy or practical.
A reaction produced by the body's immune system when exposed to a normally harmless substance.
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.
Where a substance causes unpleasant symptoms, such as diarrhoea, but does not involve the immune system.
People with an intolerance to certain foods can typically eat a small amount without having any problems.
Very occasionally, a severe reaction called anaphylaxis can occur.