Some food allergies cause immediate symptoms whereas in others it takes much longer for symptoms to develop.
The most common type of allergic reaction to food is known as an IgE-mediated food allergy.
In this type of allergy the symptoms develop very quickly after eating the allergy-causing food (the allergen); typically within a few minutes or in some cases, seconds.
In some cases a severe food allergy (anaphylaxis) can be triggered after eating a certain food and then going on to exercise vigorously. This is known as food-dependent exercise-induced anaphylaxis.
A less common type of allergic reaction is known as an non IgE-mediated food allergy. In this type of allergy the symptoms take much longer to develop after eating the allergen; usually several hours or in some cases days.
Some symptoms match what you would expect to see in an allergic reaction, such as:
Other symptoms can be much less obvious and easily mistaken 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 often happens to children who have a milk allergy.
The symptoms of a severe anaphylactic reaction usually develop within a few minutes to an hour after exposure. They can be sudden and rapidly worsen.
Initial symptoms of anaphylaxis are often the same as above and can lead to:
Anaphylaxis is a medical emergency and, without prompt treatment can be life-threatening.
Dial for an ambulance with a paramedic if you think that you or someone you know is experiencing anaphylaxis.
A food allergy is caused when your immune system mistakenly treats harmless proteins found in certain foods as a threat to your health. It then releases a number of chemicals which triggers 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 then signal to your immune system to release chemicals to kill the threat and prevent the spread of infection.
In the most common type of food allergy a type of antibody known as immunoglobulin E (IgE) mistakenly targets a certain protein found in food as a threat to your body. IgE releases several chemicals, 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 into your blood. This causes the wide range of symptoms associated with anaphylaxis.
There is another type of food allergy known as an non-IgE-mediated food allergy.
In this type of allergic reaction the immune response is largely confined to the digestive system and skin, which can cause symptoms such as heartburn, indigestion and eczema. In babies, an non-IgE-mediated food allergy can also cause diarrhoea and reflux (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, potentially any type of food can cause an allergy.
Allergic reactions have been reported in association with:
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 fruit and vegetables.
Sulphur dioxide is produced naturally when wine and beer are made. It is often added to wine to stop it from continuing to ferment in the bottle. Usually, most of the 'head space' in a bottle of wine (the part of the bottle not filled with wine) is sulphur dioxide.
Anyone who has asthma may react to inhaling sulphur dioxide. A few people with asthma have had an attack after drinking acidic drinks containing sulphites, but this is not 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 from growing, most commonly in soft drinks. They occur naturally in fruit and honey.
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 disease, such as asthma, eczema or a food allergy, you are at a higher risk of developing a food allergy. However, you may not develop the same food allergy as your family members.
Children who are born with other allergic conditions, such as asthma or atopic dermatitis (eczema, an allergic skin condition) are more likely to develop a food allergy.
Another puzzling aspect of food allergies is that the number of cases has risen sharply over the past two decades. For example, the number of children admitted to hospital for food-related anaphylaxis has risen by seven-fold since 1990.
One theory is that the rise in cases is due to the changes in a typical child’s diet that has occurred over the last 30 to 40 years.
Another theory is that children are increasingly growing up in "germ-free" environments. This means that their immune system may not receive sufficient early exposure to the germs it needs to develop properly. This is known as the hygiene hypothesis.
If you think you or your child has a food allergy, make an appointment to visit your doctor.
It is likely that your doctor will ask you some questions about the pattern of your child’s symptoms, such as:
They will also want to know about your child’s medical history, such as:
Your doctor may also asses your child’s weight and size to make sure that they are growing at the expected rate.
If your doctor suspects that you or your child has a food allergy, you may be referred to an allergy clinic or centre for testing.
If your child had symptoms that came on quickly (an IgE-mediated food allergy) then it is likely that they will be given what is known as a skin-prick test. The doctor may also want to give them a blood test.
If your child’s symptoms developed more slowly (non-IgE-mediated food) then it is likely that they will be put on what is known as a food elimination diet.
More information on these types of test is given below.
During a skin-prick test, drops of diluted foods are placed on the arm. The skin is then pierced, through the drop, using a small needle or pin to introduce the food drops to the system. Itching, redness and swelling would usually indicate a positive reaction. This is usually painless.
A skin-prick test does have a small chance of causing anaphylaxis, so testing should only be carried out where there are facilities available to deal with an anaphylactic reaction. This would usually be at an allergy clinic or centre, hospital or a larger doctor surgery.
An alternative to a skin-prick test is a blood test to measure the amount of allergic antibodies in the blood.
In a food elimination diet, the food suspected of causing the allergic reaction is withdrawn from your or your child’s diet for two to six weeks. The food is then reintroduced into the diet.
If your child’s symptoms go away when the food is withdrawn and then return once the food is introduced then this can normally confirm your child has a food allergy.
You should be given advice from a dietitian, before starting the diet, on issues such as:
Do not attempt a food-elimination diet by yourself without discussing it with a qualified health professional.
There are several shop-bought tests available which claim to detect allergies. They include:
Many alternative testing kits are expensive, the scientific principles they are alleged to be based on are unproven and independent tests have been found to be unreliable. They should therefore be avoided.
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, a protein responsible for most of the symptoms of an allergic reaction.
Many antihistamines are available from your pharmacist without prescription so it may be a good idea to stock up in case of an emergency.
Some antihistamines, such as alimemazine and promethazine, aren't suitable for children under two years old. Therefore seek advice from your doctor if you have a younger child with a food allergy about what types of antihistamines may be suitable.
Avoid drinking alcohol after taking an antihistamine as this can make you feel drowsy.
Adrenaline works by narrowing the blood vessels to counteract the effects of low blood pressure, and by opening up the airways to help ease breathing difficulties.
If your child’s, or your own allergies, are thought have a potential risk of anaphylaxis or has had a previous episode of anaphylaxis, you will be given an auto-injector of adrenaline to use in case of emergencies.
Carefully read the manufacturer’s instructions that come with the auto-injector and when your child is old enough, train them how to use it (see below).
If you suspect that somebody is experiencing the symptoms of anaphylaxis then immediately call 999 for an ambulance and 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 then you should remove the safety cap from the injector, place it against your outer thigh (holding it as a right angle) and then hold down the firing button that is located at the end of the injector. The injections can be given through clothing.
This will send a needle into your thigh and deliver a dose of adrenaline. You need to hold the button down for ten seconds.
If the person is unconscious, check their airways are open and clear and check their breathing. Then put them in the recovery position (see below). Putting someone who is unconscious in the recovery position ensures that they do not choke on their vomit.
Place the person on their side, ensuring that they are 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 is strongly recommended.
Sheila, 69 from Bedfordshire, has lived with a fish allergy for most of her life
“Every time I had fish as a baby, I vomited. But at that time, allergies were not widely recognised so my mum carried on giving it to me. If I was ever given fresh fish, I always vomited, had bad pains in my stomach and sometimes fainted.
“I can eat fish that is tinned or smoked, but any other form of fish makes me very ill. Throughout my life, I have simply avoided eating fish. There is no other treatment. The best method is to avoid it.
“I have to be very careful in restaurants. I always have to explain my allergy when I go to a restaurant and I have to make sure my food is not cooked with fish. Food labels now state allergens more clearly so I always check labels too.
“The worst experience with my allergy was when I ate paella in a restaurant. I didn’t realise there was fish in it and I vomited and passed out in the middle of the restaurant.
“My advice to anyone with a food allergy is to see your doctor and take any tests that are offered so you know exactly what you're allergic to. Always check labels carefully and be vigilant in restaurants, at weddings and any other social functions.”
The advice below is primarily written for parents of a child with a food allergy but much of it will also apply to you if you are an adult with a food allergy.
There is currently no cure for food allergies, although many children will grow out of them. The most effective way you can prevent symptoms is to remove the offending food (the allergen) from their diet.
However, it's important to check first with your doctor or the doctor in charge of your child’s care before eliminating certain foods.
If their allergy is to eggs or peanuts than removing either from them is not going to have much of an impact on their nutrition. Both types of food are a good source of protein but there are many other alternative sources of protein.
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 include calcium in your child’s diet, such as green leafy vegetables.
Many foods and drinks are fortified with extra calcium.
If you are concerned that your child’s allergy is affecting their growth and development then contact your doctor for advice.
It is very important that you read the list of ingredients on the label of any pre-packed food or drinks your child has.
Under EU law, any pre-packed food or drink sold in Europe 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 that is known to commonly cause an allergic reaction, such as peanuts, eggs or milk.
However, these are not compulsory. If there is no allergy advice box or "contains" statement on a product, it doesn't mean that none of the 14 specified allergens are used as ingredients.
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.
Some non-food products contain allergy-causing food:
Again, read the labels of any non-food products that 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, and therefore it can be more difficult for to know what ingredients are used in a particular dish.
Examples of unpackaged food include food sold from:
If your child has a severe food allergy, you will need to be careful if you want to eat out with them.
The following advice should help:
Further advice for parents is provided below.
Jane is mother to Lilly, born in 1997, who developed multiple allergies in her first few months of life. This is Jane and Lilly’s story.
"Lilly had breathing and feeding difficulties as soon as she was born. She struggled to take anything in, brought up most of it and had extreme colic. Her bowel movements were very loose, yellow and pungent. She only gained 7oz in the first eight weeks. At 10 weeks, I took her to my doctor because my instinct told me something was seriously wrong. Over the next five months, these visits became quite regular.
"Lilly was diagnosed with gastroenteritis 12 times and received replacement fluids followed by a re-introduction of milk. When milk was re-introduced, it was barely a few hours before her symptoms re-emerged, each time becoming more aggressive.
"We were referred to the local hospital, where it was suggested that Lilly may be intolerant to milk. She was swapped to soya-based infant formula, but her symptoms didn't improve.
"At nine months, Lilly became seriously ill. Her faeces had turned to jelly, she was pale and clammy and we couldn't wake her. We rushed her to hospital and the consultant told us our daughter was probably suffering from an allergy to her feed. Over the next few weeks, she was nasally fed with clear fluids and through a drip until her symptoms subsided.
"Once she was stable, milk and soya were both re-introduced separately and Lilly reacted to both. At this point, she was started on Neocate, an amino-acid-based formula for highly allergic infants. Her gastroenterologist explained that her system would take some time to settle as it had taken so long to reach a diagnosis.
"Over the next three years, Lilly underwent vast amounts of tests, food challenges and scans. She spent long periods in hospital on drips and nasal feeding as her system was too weak to cope with normal childhood illnesses. It took two years for her system to calm down, and she remains severely allergic to all milk products, soya, eggs, nuts, mango and some antibiotics.
"As she grows up, policing Lilly's every move becomes more difficult each year. We can only hope that, with guidance and an exact understanding of her allergies, she will stay safe.
"When asked now what parents should do if they think their child may have a food allergy, I always tell them to listen to their instincts and I refer them to Allergy UK, which has been an amazing source of support."
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:
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 for an ambulance and tell the operator that you think the person has anaphylaxis.
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:
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:
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.
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 doctor.
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.
If you suspect you or your child may have a food allergy, it's very important to ask for a professional diagnosis from your doctor, who can refer you to an allergy clinic.
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.
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.
Alexis Manning, 32, is a fourth-year medical student at Cardiff University. He has been allergic to peanuts for most of his life
"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 a 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 try to manage young children with severe food allergies. Because of this, I set up a website called Peanut Allergy UK, which gives basic information to people with a peanut allergy and contains a discussion forum to allow them to talk with other sufferers about issues such as safe foods, travelling and school.
"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."
Important: Our website provides useful information but is not a substitute for medical advice. You should always seek the advice of your doctor when making decisions about your health.