A food allergy is when the body's immune system reacts abnormally to specific foods.
Allergic reactions are often mild, but they can sometimes be very serious.
In children, common food allergies include being allergic to milk and eggs. In adults, allergies to fruits and vegetables are more common. Nut allergies, such as being allergic to peanut, are relatively common in both children and adults.
Symptoms of a food allergy can affect different areas of the body at the same time. Some common symptoms include:
- an itchy sensation inside the mouth, throat or ears
- raised itchy red skin rash (this is known as urticaria, hives or "nettle rash")
- swelling of the face, around the eyes, lips, tongue and the roof of the mouth (this is known as angioedema)
Read more about the symptoms of food allergies.
In the most serious cases, a person has a severe allergic reaction (anaphylaxis), which can be life-threatening.
If you suspect that somebody is experiencing the symptoms of anaphylaxis, such as breathing difficulties and swollen lips, immediately call 999 for an ambulance and tell the operator that you think the person has anaphylaxis.
What causes food allergies?
Food allergies are caused when the immune system (the body’s defence against infection) mistakenly treats proteins found in food as a threat to the body, when in fact they should be harmless.
It then releases a number of chemicals to prevent what it sees as an infection taking hold. It is these chemicals that cause the symptoms of an allergic reaction.
Any food could cause an allergic reaction, but there are certain foods that are responsible for most food allergies.
In children, the foods that most commonly cause an allergic reaction are:
- tree nuts
The majority of children with a food allergy have a background of eczema (an allergic skin condition) during infancy. The worse their eczema is and the earlier it started, the more likely they are to have a food allergy.
In adults, the foods that most commonly cause an allergic reaction are:
- some types of fruit such as apples, pears, kiwi fruit and peaches
- some types of vegetables such as potatoes, carrots, celery and parsnip
- crustaceans (shellfish), such as crab, lobster and prawns
- tree nuts, such as walnuts, brazil nuts, almonds and pistachios
It is still uncertain why people develop allergies to food, although often people with a food allergy have other allergic conditions such as asthma, hay fever and eczema.
Read more information about the causes and risk factors for food allergies.
Types of food allergies
The most common type of food allergy is triggered by an antibody called immunoglobulin E. This is known as IgE-mediated food allergy and tends to cause rapid symptoms, often within seconds or minutes of exposure to certain foods. There is a greater risk of anaphylaxis with this type of allergy.
Allergic reactions not caused by immunoglobulin E (non IgE mediated food allergy) tend to cause symptoms hours or even days after exposure to certain foods. This type of allergy is often difficult to diagnose.
There is no treatment to cure a food allergy. The best way of preventing an allergic reaction is to identify the type of food that causes the allergy and then avoid it in future.
Read more about identifying foods which cause allergies (these are known as allergens).
However, avoid making any radical changes to your child’s diet, such as cutting dairy products, without first consulting with your GP.
A type of medication called an antihistamine can help relieve the symptoms of a mild to moderate allergic reaction. A type of medication called adrenaline is an effective treatment for anaphylaxis.
People with a food allergy are often given a device, known as an auto-injector pen, which contains dosages of adrenaline that can be used in case of emergencies.
Read more about the treatment of food allergies.
When to seek medical advice
If you suspect you or your child may have a food allergy, it's very important to ask for a professional diagnosis from your GP, who can refer you to an allergy clinic.
The National Institute for Health and Clinical Excellence has also released a short guide for parentss (PDF, 104kb) who are concerned that their child has a food allergy.
Many parents mistakenly assume their child has a food allergy when in fact their symptoms are due to a completely different condition.
There are commercial allergy-testing kits available but their use is not recommended. Many kits are based on unsound scientific principles and even if they are reliable, it is best to have the results interpreted by a health professional.
Read more about diagnosing food allergies.
Who is affected
Most food allergies affect younger children aged under the age of three. It is estimated that around one child in every 14 children of this age has one or more food allergies.
Most children will "outgrow" food allergies to milk, eggs, soya and wheat by the time they start school.
Peanut allergies are usually more persistent. An estimated four out of five children with peanut allergies remain allergic to peanuts for the rest of their life.
Food allergies that develop during adulthood, or persist into adulthood, are likely to be lifelong allergies.
For reasons that are unclear, rates of food allergies have risen sharply in the last 20 years.
However, deaths from anaphylaxis-related food reactions are now very rare. There were only two reported deaths related to food allergies in England and Wales during 2010.