Health A to Z
A food allergy is when the body's immune system reacts unusually to specific foods. Although allergic reactions are often mild, they can be very serious.
Symptoms of a food allergy can affect different areas of the body at the same time. Some common symptoms include:
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 think someone has the symptoms of anaphylaxis – such as breathing difficulties, lightheadedness, and feeling like they're going to faint or lose consciousness – call 999.
Ask for an ambulance and tell the operator you think the person has anaphylaxis or "anaphylactic shock".
Food allergies happen when the immune system – the body's defence against infection – mistakenly treats proteins found in food as a threat.
As a result, a number of chemicals are released. It's these chemicals that cause the symptoms of an allergic reaction.
Almost any food can 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:
Most children that have a food allergy will have experienced eczema during infancy. The worse the child's eczema 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:
Read more information about the causes and risk factors for food allergies.
Food allergies are divided into three types, depending on symptoms and when they occur.
Read more information about the symptoms of a food allergy.
Some people experience itchiness in their mouth and throat, sometimes with mild swelling, immediately after eating fresh fruit or vegetables. This is known as oral allergy syndrome.
Oral allergy syndrome is caused by allergy antibodies mistaking certain proteins in fresh fruits, nuts or vegetables for pollen.
Oral allergy syndrome generally doesn't cause severe symptoms, and it's possible to deactivate the allergens by thoroughly cooking any fruit and vegetables.
Some people with pollen-food syndrome may have more severe symptoms.
The Allergy UK website has more information.
The best way of preventing an allergic reaction is to identify the food that causes the allergy and avoid it.
Research is currently looking at ways to desensitise some food allergens, such as peanuts and milk, but this is not an established treatment.
Read more about identifying foods that cause allergies (allergens).
Avoid making any radical changes, such as cutting out dairy products, to your or your child's diet without first talking to your GP. For some foods, such as milk, you may need to speak to a dietitian before making any changes.
A type of medication called an antihistamine can help relieve the symptoms of a mild or moderate allergic reaction. A higher dose of antihistamine is often needed to control acute allergic symptoms.
Adrenaline is an effective treatment for more severe allergic symptoms, such as anaphylaxis.
People with a food allergy are often given a device known as an auto-injector pen, which contains doses of adrenaline that can be used in emergencies.
Read more about the treatment of food allergies.
If you think you or your child may have a food allergy, it's very important to ask for a professional diagnosis from your GP. They can then refer you to an allergy clinic if appropriate.
Many parents mistakenly assume their child has a food allergy when their symptoms are actually caused by a completely different condition.
Commercial allergy testing kits are available, but using them isn't recommended. Many kits are based on unsound scientific principles. Even if they're reliable, you should have the results looked at by a health professional.
Read more about diagnosing food allergies.
Most food allergies affect younger children under the age of three. It's estimated around 1 in every 14 children of this age has at least one food allergy.
Most children who have food allergies to milk, eggs, soya and wheat in early life will grow out of it by the time they start school.
Peanut and tree nut allergies are usually more persistent. An estimated four out of five children with peanut allergies remain allergic to peanuts for the rest of their lives.
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 rare. There are around 10 deaths related to food allergies in England and Wales each year.
The symptoms of a food allergy almost always develop a few seconds or minutes after eating the food.
Some people may develop a severe allergic reaction (anaphylaxis), which can be life threatening.
The most common type of allergic reaction to food is known as an IgE-mediated food allergy.
The symptoms of a severe allergic reaction (anaphylaxis) can be sudden and get worse very quickly.
Initial symptoms of anaphylaxis are often the same as those listed above and can lead to:
Anaphylaxis is a medical emergency. Without quick treatment, it can be life threatening. If you think you or someone you know is experiencing anaphylaxis, dial 999 and ask for an ambulance as soon as possible.
Another type of allergic reaction is a non-IgE-mediated food allergy. The symptoms of this type of allergy can take much longer to develop – sometimes up to several days.
Some symptoms of a non IgE-mediated food allergy may be what you would expect to see in an allergic reaction, such as:
Other symptoms can be much less obvious and are sometimes thought of as being caused by something other than an allergy. They include:
Some children can have a mixed reaction where they experience both IgE symptoms, such as swelling, and non-IgE symptoms, such as constipation.
This can happen to children who have a milk allergy.
A food allergy is caused by your immune system handling harmless proteins in certain foods as a threat. It releases a number of chemicals, which trigger an allergic reaction.
The immune system protects the body by producing specialised proteins called antibodies.
Antibodies identify potential threats to your body, such as bacteria and viruses. They signal your immune system to release chemicals to kill the threat and prevent the spread of infection.
In the most common type of food allergy, an antibody known as immunoglobulin E (IgE) mistakenly targets a certain protein found in food as a threat. IgE can cause several chemicals to be released, the most important being histamine.
Histamine causes most of the typical symptoms that occur during an allergic reaction. For example, histamine:
In most food allergies, the release of histamine is limited to certain parts of the body, such as your mouth, throat or skin.
In anaphylaxis, the immune system goes into overdrive and releases massive amounts of histamine and many other chemicals into your blood. This causes the wide range of symptoms associated with anaphylaxis.
There's another type of food allergy known as a non-IgE-mediated food allergy, caused by different cells in the immune system.
This is much harder to diagnose as there's no test to accurately confirm non-IgE-mediated food allergy.
This type of reaction is largely confined to the skin and digestive system, causing symptoms such as heartburn, indigestion and eczema.
In babies, a non-IgE-mediated food allergy can also cause diarrhoea and reflux, where stomach acid leaks up into the throat.
In children, the foods that most commonly cause an allergic reaction are:
In adults, the foods that most commonly cause an allergic reaction are:
However, any type of food can potentially cause an allergy. Allergic reactions have been reported in association with:
Exactly what causes the immune system to mistake harmless proteins as a threat is unclear. However, a number of risk factors for food allergies have been identified, which are outlined below.
If you have a parent, brother or sister with an allergic condition – such as asthma, eczema or a food allergy – you have a slightly higher risk of developing a food allergy. However, you may not develop the same food allergy as your family members.
Children who have atopic dermatitis (eczema) in early life are more likely to develop a food allergy.
The number of people with food allergies has risen sharply over the past few decades and, although the reason is unclear, other allergic conditions such as atopic dermatitis have also increased.
One theory behind the rise is that a typical child's diet has changed considerably over the last 30 to 40 years.
Another theory is that children are increasingly growing up in "germ-free" environments. This means their immune systems may not receive sufficient early exposure to the germs needed to develop properly. This is known as the hygiene hypothesis.
It's rare for someone to have an allergic reaction to food additives. However, certain additives may cause a flare-up of symptoms in people with pre-existing conditions.
Sulphur dioxide (E220) and other sulphites (E221, E222, E223, E224, E226, E227 and E228) are used as preservatives in a wide range of foods, especially soft drinks, sausages, burgers, and dried fruits and vegetables.
A few people with asthma have had an attack after drinking acidic drinks containing sulphites, but this isn't thought to be very common.
Food labelling rules require pre-packed food sold in the UK, and the rest of the European Union, to show clearly on the label if it contains sulphur dioxide or sulphites at levels above 10mg per kg or per litre.
Benzoic acid (E210) and other benzoates (E211, E212, E213, E214, E215, E218 and E219) are used as food preservatives to prevent yeasts and moulds growing, most commonly in soft drinks. They occur naturally in fruit and honey.
Benzoates could make the symptoms of asthma and eczema worse in children who already have these conditions.
If you think you or your child has a food allergy, make an appointment with your GP.
They will ask you some questions about the pattern of your child's symptoms, such as:
They'll also want to know about your child's medical history, such as:
Your GP may also assess your child's weight and size to make sure they're growing at the expected rate.
If your GP suspects a food allergy, you may be referred to an allergy clinic or centre for testing.
The tests needed can vary, depending on the type of allergy:
There is more information on these tests below.
During a skin-prick test, drops of standardised extracts of foods are placed on the arm. The skin is then pierced with a small lancet, which allows the allergen to come into contact with the cells of your immune system.
Occasionally, your doctor may perform the test using a sample of the food thought to cause a reaction.
Itching, redness and swelling usually indicates a positive reaction. This test is usually painless.
A skin-prick test does have a small theoretical chance of causing anaphylaxis, but testing will be carried out where there are facilities to deal with this – usually an allergy clinic, hospital, or larger GP surgery.
An alternative to a skin-prick test is a blood test, which measures the amount of allergic antibodies in the blood.
In a food elimination diet, the food thought to have caused the allergic reaction is withdrawn from the diet for two to six weeks. The food is then reintroduced.
If the symptoms go away when the food is withdrawn but return once the food is introduced again, this normally suggests a food allergy or intolerance.
Before starting the diet, you should be given advice from a dietitian on issues such as:
Don't attempt a food elimination diet by yourself without discussing it with a qualified health professional.
There are several shop-bought tests available that claim to detect allergies, but should be avoided.
Many alternative testing kits are expensive, the scientific principles they are allegedly based on are unproven, and independent reviews have found them to be unreliable. They should therefore be avoided.
The advice here is primarily written for parents of a child with a food allergy. However, most of it is also relevant if you're an adult with a food allergy.
There's currently no cure for food allergies, although many children will grow out of certain ones, such as allergies to milk and eggs.
The most effective way you can prevent symptoms is to remove the offending food – known as an allergen – from their diet.
However, it's important to check with your GP or the doctor in charge of your child's care first before eliminating certain foods.
Removing eggs or peanuts from a child's diet isn't going to have much of an impact on their nutrition. Both of these are a good source of protein, but can be replaced by other, alternative sources.
A milk allergy can have more of an impact as milk is a good source of calcium, but there are many other ways you can incorporate calcium into your child's diet, including green leafy vegetables. Many foods and drinks are fortified with extra calcium.
See your GP if you're concerned that your child's allergy is affecting their growth and development.
It's very important to check the label of any pre-packed food or drinks your child has in case it contains ingredients they're allergic to.
Under EU law, any pre-packed food or drink sold in the UK must clearly state on the label if it contains the following ingredients:
Some food manufacturers also choose to put allergy advice warning labels – for example, "contains nuts" – on their pre-packed foods if they contain an ingredient known to commonly cause an allergic reaction, such as peanuts, wheat, eggs or milk.
However, these aren't compulsory. If there's no allergy advice box or "contains" statement on a product, it could still have any of the 14 specified allergens in it.
Look out for "may contain" labels, such as "may contain traces of peanut". Manufacturers sometimes put this label on their products to warn consumers that they may have become contaminated with another food product when being made.
Read more detailed information about allergen labelling on the Food Standards Agency website.
Some non-food products contain allergy-causing food:
Again, read the labels of any non-food products your child may come into close physical contact with.
Currently, unpackaged food doesn't need to be labelled in the same way as packaged food. This can make it more difficult to know what ingredients are in a particular dish.
Examples of unpackaged food include food sold from:
If you or your child have a severe food allergy, you need to be careful when you eat out.
The following advice should help:
Here's some more advice for parents:
There are two main types of medication that can be used to relieve the symptoms of an allergic reaction to foods:
Antihistamines work by blocking the effects of histamine, which is responsible for many of the symptoms of an allergic reaction.
Many antihistamines are available from your pharmacist without prescription – stock up in case of an emergency. Non-drowsy antihistamines are preferred.
Some antihistamines, such as alimemazine and promethazine, aren't suitable for children under the age of two.
If you have a younger child with a food allergy, ask your GP about what types of antihistamines may be suitable.
Avoid drinking alcohol after taking an antihistamine as this can make you feel drowsy and affect your ability to drive.
Adrenaline works by narrowing the blood vessels to counteract the effects of low blood pressure and opening up the airways to help ease breathing difficulties.
You'll be given an auto-injector of adrenaline to use in case of emergencies if you or your child is at risk of anaphylaxis or had a previous episode of anaphylaxis.
Read the manufacturer's instructions that come with the auto-injector carefully and train your child how to use it when they are old enough.
If you suspect that somebody is experiencing the symptoms of anaphylaxis, call 999 and ask for an ambulance. Tell the operator that you think the person has anaphylaxis.
Older children and adults will probably have been trained to inject themselves. You may need to inject younger children or older children and adults who are too sick to inject themselves.
There are three types of auto-injectors:
All three work in much the same way. If anaphylaxis is suspected, you should remove the safety cap from the injector and press firmly against the thigh, holding it at a right angle, without using the thumb at the end.
A "click" indicates the auto-injector has been activated, and it should be held in place for 10 seconds. Ensure you're familiar with the device and know the correct end to place against the thigh.
The injections can be given through clothing. This will send a needle into your thigh and deliver a dose of adrenaline.
If the person is unconscious, check their airways are open and clear, and check their breathing. Then put them in the recovery position. Putting someone who is unconscious in the recovery position ensures they don't choke on their vomit.
Place the person on their side, making sure they're supported by one leg and one arm. Open the airway by tilting the head and lifting the chin.
If the person's breathing or heart stops, cardiopulmonary resuscitation (CPR) should be performed.
As a precaution, the following advice should be taken:
Alexis Manning has a peanut allergy.
"I first found out that I was allergic to peanuts as a child. Some sweets just tasted bad and made my lips swell a bit, and it didn’t take long to work out the cause. I didn't have testing at the time because peanut allergies weren't very common, and it didn't seem too severe. I avoided peanuts, but the reactions got worse.
"I had my first anaphylactic reaction when I was 18, while eating a salad that contained things that looked like baked beans, but were actually peanuts. I ate one of these – the most peanut I'd ever had at one time, I think – and immediately knew something was very wrong. Within minutes, my face swelled up. My skin felt tight, I couldn't close my eyes, I couldn't hear properly and, worst of all, I couldn't breathe.
"I was lucky that the nearest hospital was only 10 minutes away. After they gave me several injections of adrenaline, medical staff were able to bring my reaction under control. I was given some EpiPens and sent on my way.
"Since then, I've been exceptionally careful about what I eat. Food labelling has improved markedly in recent years, but many foods still seem to have 'may contain' warnings that seem unlikely. For example, I've seen fish, red cabbage and sour cream all marked with 'may contain peanuts'.
"I also make sure I carry a couple of EpiPens with me at all times, but have never had to use them because I'm very, very careful. It can be socially awkward. I've had to give up eating out after being caught out on more than one occasion at restaurants where the language barrier was an issue. Also, I find it generally less stressful if I simply don't eat anything I haven't prepared myself. People who know me accept this, but others find it a bit odd if everyone's sitting down to a meal and I'm there with an empty plate not eating.
"I consider myself lucky, odd though it might sound. Some people experience anaphylactic reactions early in childhood, but I only had to deal with it when I was old enough to look after myself. I have a lot of sympathy for parents who have to manage young children with severe food allergies.
"My advice for people newly diagnosed with a peanut allergy is not to panic. Initially, it seems like you can't eat anything, but food labelling has improved massively over the last few years, so being vigilant has become easier."