Food allergy

Expert reviewer Dr Alexander Alexandroff, Consultant Dermatologist
Next review due September 2021

A food allergy is when your body’s immune system, which usually fights infections, overreacts to one or more foods. This can make you feel unwell. If your allergy is severe, it can be life-threatening. You may have a reaction to a food, such as eggs or nuts, every time you eat it.

About five in 100 children have a food allergy. Among adults, about three or four in every 100 have a food allergy. Some children lose an allergy to foods such as milk and eggs as they grow up. But it’s unusual to lose an allergy to peanuts, seafood, fish or tree nuts.

Healthy smmothie and bananas

Common foods that cause an allergic reaction

Any protein in a food can cause a reaction, but there’s a small group of foods that cause most allergic reactions.

  • Cow’s milk. This is more common in children than in adults and many children grow out of it by the age of five.
  • Eggs. An allergy to eggs is more common in children and it usually starts before a baby is a year old. Some people can eat well-cooked egg, but not raw or loosely cooked egg.
  • Peanuts and tree nuts. Tree nuts include almonds, cashews and walnuts.

Other foods can cause allergies too, such as:

  • sesame seeds
  • fish and shellfish
  • soya
  • fruit, including kiwi fruit
  • wheat – although people who react to wheat may have a bowel condition called coeliac disease rather than an allergy

Some people can have a cross-reaction between foods. So for example, if you’re allergic to cow’s milk you’re likely to be allergic to goat’s milk too. If you’re allergic to peanuts you may also react to other members of the pea family, including lupin. Lupin flour and seeds are sometimes used in bread, pastry and pasta and in wheat and gluten-free food.

Symptoms of food allergy

The symptoms of a food allergy can come on very quickly, usually within 20 minutes after you’ve eaten the food. You may need to eat only a small amount of something for it to cause a reaction. You may have some of the following symptoms:

  • a runny, blocked or itchy nose and sneezing
  • itchy, red and swollen skin and a rash
  • sore, red, swollen or itchy eyes
  • wheezing, a cough, noisy breathing or shortness of breath
  • diarrhoea
  • feeling sick or being sick
  • feeling bloated (swollen abdomen) with tummy pains (cramps)

These symptoms could also be caused by other conditions and illnesses. Speak to your GP if you have any of these symptoms.

Severe reactions

Food allergies can also cause a severe allergic reaction called anaphylaxis, which affects your whole body. This can be life-threatening and needs treating straightaway. If the symptoms of an allergic response become severe and your mouth and throat swell, your airway can become blocked which can be very serious. If someone is having trouble breathing or is losing consciousness, call 999 immediately.

An infographic showing the symptoms of food allergy

Diagnosis of food allergy

Your GP will ask you about your allergic reaction, what the symptoms are, how quickly they develop, and how severe they are. Your GP may also ask you about the foods you ate in the two hours before the reaction, what these were and how much of them you ate. You might be asked to keep a food diary too.

If your GP thinks you have a food allergy, they may refer you for tests to see what kind of reaction it is, and to confirm whether the foods suspected are causing it. Common allergy tests are listed below.

  • Skin prick tests. A tiny amount of a food is put onto your skin, on its own or mixed in a liquid. A needle is used to prick through it to pierce your skin. If you’re allergic to the food, you’re likely to get a skin reaction called a wheal after about 20 minutes.
  • Blood tests. These measure the amount of antibodies to different food proteins. The antibodies are called immunoglobulin E (IgE).
  • Food challenges. This is when you’re given increasing amounts of certain foods to eat to see if you have a reaction. This test should always be done in a place where you can be safely treated if necessary.

For some types of allergic reaction, you may be asked to try an elimination diet over two to six weeks. This is when you stop eating the food or foods that may be causing your allergic reaction to see whether your symptoms get better. If they do, you’ll be asked to start eating the food again to see if your symptoms come back.

Other tests, such as applied kinesiology, hair analysis and vega testing are sometimes advertised as a way of testing for food allergies. But, there’s no evidence to show that these work, so they’re not recommended for diagnosing food allergies.

Treatment of food allergy

The main treatment for food allergy is to not eat the food that you’re allergic to. This is especially important if your allergy is severe and a small amount of the food could start a reaction. You may also need to be careful about inhaling or touching foods that you’re allergic to.

You should be given advice about how to read food labels, what foods to avoid and how to eat safely when you’re not at home. You may be referred to a dietitian who can give you specific advice. For information about avoiding trigger foods, see the section about living with a food allergy further down the page.

If your allergy is mild and you only have symptoms such as itching or a rash, your doctor may suggest taking antihistamines as soon as an allergic reaction starts. Your doctor may also suggest taking medicine called an H2 antagonist, such as ranitidine. This works well with the antihistamine to reduce the allergic reaction and your symptoms.

If your symptoms include wheezing or breathing problems, you might be given a medicine called a bronchodilator to take. You should breathe this in from an inhaler when the allergic reaction starts, and then several times over the next hour or longer depending on your symptoms. Your doctor will tell you how much to take and when.

Injectable adrenaline

If you’re likely to have a severe allergic reaction to a food, your doctor may prescribe injectable adrenaline which you can give yourself. You might hear this called an EpiPen®.

If you accidentally eat or touch a food which causes a severe allergic reaction you can give yourself the adrenaline straightaway, or someone can give it to you. You’ll be shown how and when to use it. Doctors usually recommend that you have two EpiPens®. If the first injection doesn’t work well enough, you can give a second injection five minutes after the first. You should always carry these with you wherever you go.

Emergency treatment for food allergy

If you’re having a severe allergic reaction and problems breathing, and you have adrenaline that you can inject yourself you should use it. Ask someone to call 999 for an ambulance immediately, even if the adrenaline seems to be settling the symptoms.

You’ll be given adrenaline and other medicines to help ease your symptoms. You may also need oxygen to help your breathing, and extra fluids which are usually given through a drip. If your condition gets worse, you may need to have a tube put into your airway to help you breathe until the allergic reaction eases.


Immunotherapy is when you’re regularly given very small amounts of the food protein that you’re allergic to. Over time, the amount you have gets bigger, so your body learns to accept the allergen. This should mean that your reaction to a food will be milder and you can have more of it before a reaction starts.

Immunotherapy is a new kind of treatment and research is still being done to test how well it works and in which people. It’s not a treatment choice for everyone with a food allergy.

Causes of food allergy

An allergy is your body's immune system reacting to something that’s usually harmless, such as foods, pollen, bee stings and house dust mite. In most people these substances (allergens) don’t cause any problems, but if you’re allergic to them your immune system sees them as a ‘threat’ and overreacts. That causes the symptoms of an allergic reaction.

There are different types of allergic reaction. With some types of allergy you’ll get a reaction straightaway and with others the reaction takes hours or days to develop. One type of allergy is atopy, which includes asthma, eczema and hay fever.

The reasons why some people have a food allergy and others don’t is complicated, but it’s usually a mix of:

  • your genetics – allergy sometimes runs in families
  • things in your environment, such as how much contact you have with infections and germs (bacteria) in your childhood

Complications of food allergy

The most severe complication of food allergy is anaphylaxis. This is a severe, full-body allergic reaction which can be life-threatening. Children are more likely to have anaphylactic reaction to a food than adults. If you’ve had a severe or an anaphylactic reaction to a food before, then you’re likely to have another one if you come into contact with the food again. But, further reactions won’t necessarily be as severe as previous ones.

If you have to cut out a lot of foods to prevent a reaction, it can affect your health generally. This is because you may not be getting all the energy and goodness (nutrients) you need. If your child has a food allergy, then changing their diet can affect how well they grow. If you need to make a lot of changes to your diet or cut out lots of foods, you should get specialist advice from a dietitian.

Living with a food allergy

If you or your child has a food allergy, you’ll need to avoid the foods that cause a reaction. The following tips may help.

  • Make sure you know exactly what foods you’re allergic too, and what these might be called on food labels. It’s also important to know what kind of symptoms you might get if you’re having an allergic reaction and have a plan for what you’ll do if it happens.
  • When you’re shopping, check the labels on foods carefully to find out whether they contain the ingredient you’re allergic to. By law, the 14 most common ingredients that can cause allergies must be listed on foods with packaging and foods without it, such as those in delis and bakeries. If you need more information, you can ask the staff. Or you can ask supermarkets and manufacturers for a copy of their ‘Free From list’ for the food you want to avoid.
  • If you have a severe allergy to a food, be aware that although many manufacturers put a warning on labels, they don’t have to say if something like nuts could accidentally get into a food.
  • If very tiny amounts of a food could give you an allergic reaction, be careful not to cross-contaminate when you’re cooking or preparing foods. This means keeping certain foods, knives, utensils and chopping boards separate and always cleaning them straightaway.
  • Take extra care when you’re eating food that you haven’t bought or made, such as in restaurants, at barbecues and parties. Tell family and friends about your allergy and check with restaurant staff which foods are okay to eat and how the food is prepared.
  • For new food and recipe ideas, check out ‘Free-From’ ranges at supermarkets. You may also find useful ideas online and through mobile phone apps.

If you’re likely to have a severe reaction to a food, your doctor may suggest you wear a medical emergency identification bracelet. If you have a reaction and become unwell quickly, the bracelet tells other people about your allergy, so you can get the right help quickly.

Frequently asked questions

  • There’s been a lot of discussion and research aimed at answering this question but, for now, there’s no clear answer. There are no proven ways to reduce the chances of your child developing a food allergy.

    Doctors don’t know what effect breastfeeding has on your baby’s chance of developing allergies but there are lots of other good reasons to breastfeed. So, it’s a good idea to follow the general advice which is to breastfeed your baby for the first six months.

    If you’re pregnant or breastfeeding, you can eat peanuts or foods containing peanuts whether you have a family history of allergies or not. But, if your child has already been diagnosed with an allergy or there is a history of allergy in the family, it’s a good idea to get advice from your GP before you give them peanuts.

    When you’re starting to give solid foods that could cause a reaction, such as nuts or eggs, introduce them one at a time. If your baby has a reaction, you’ll be able to notice any symptoms.

  • Food allergies and food poisoning can have similar symptoms, so it can be hard to tell which is causing your symptoms.

    Diarrhoea, feeling or being sick and abdominal (tummy) discomfort can all be symptoms of both food allergy and food poisoning. But there are some symptoms of food poisoning that are different from food allergy and vice versa. Food allergy symptoms often affect other parts of your body, such as your skin, eyes, nose and lungs as well as your stomach and bowels, If you have food poisoning, you’ll probably have a fever too.

    Because it’s difficult to tell the two apart, it’s best to speak to your GP and get medical advice if you’re worried.

  • Although it’s possible to come into contact with peanuts on a flight, it’s rare for someone to have a severe allergic reaction. It’s unlikely that peanut allergen will be moved around the cabin through the air-conditioning. But passengers seated close to you may eat peanuts or there may be traces of it on surfaces such as your tray table. Even though the risks are small, it makes sense to plan and take steps to reduce your chances of having a reaction. Here are some helpful tips.

    • Ask the airline to arrange a special meal for you and make sure you arrange that for any connecting flights too. Mistakes do sometimes happen so check a meal has been arranged when you check in for your flight and when you get on the plane. If you want to be extra safe, take your own food with you.
    • Use alcohol wipes to clean your tray table and any surface that may have been touched by other passengers.
    • If you’re severely allergic to peanuts, you can choose an airline that doesn’t serve peanuts at all. Other airlines will sometimes remove peanut snacks on the flight you’re on if you give them enough notice.
    • Tell the cabin staff that you have a severe peanut allergy when you board the plane.
    • Before you fly, get a letter from your doctor explaining why your adrenaline injector needs to be in your hand luggage. Take any medicines you have been prescribed on the plane with you (such as antihistamines or an adrenaline injector). If you’re severely allergic, keep your injectable adrenaline with you (not in the overhead locker) and tell anyone you’re travelling with, or the cabin crew, where it is.

  • If you have a peanut allergy, you’re unlikely to have an allergic reaction to refined peanut oil. This should have all the allergen taken out of it, but it can be hard to know whether it’s been done well enough. So, it’s best not to eat or use anything with refined peanut oil in it.

    You could react to unrefined peanut oil so it’s best not to eat or use products with this in it. It’s sometimes used in South Asian food and is also called groundnut oil.

  • Most vaccines aren’t made using eggs so they’re safe to have if you have an egg allergy. But there are three vaccinations made using a part of a hen’s egg:

    • Measles, mumps and rubella. This is made using extremely small amounts of egg protein and it’s been shown to be safe when given to babies and children with an egg allergy. So, if your child has an egg allergy, they can still have the MMR vaccination.
    • Yellow fever. It’s possible for people with a severe egg allergy to have a reaction to the yellow fever vaccination. So, if you need this vaccination get advice from an allergy specialist.
    • Influenza (flu). Some influenza (flu) vaccines are made using eggs, but others have extremely low amounts of egg in them. If you’ve had a severe (anaphylactic) reaction to egg before, you should get advice from an allergy specialist before having the flu vaccine.

  • No, a food intolerance is different from a food allergy. Food allergy reactions involve your immune system, whereas a food intolerance doesn’t – it involves your digestive system.

    Food intolerances aren’t usually life-threatening, but they can make you feel very unwell and have a major impact on both your physical and mental health. Food intolerance is when your body can’t properly breakdown a food. This could be because your body doesn’t have enough of certain enzymes, because of a sensitivity to food additives or a reaction to natural chemicals in foods. Common foods which can cause food intolerance include:

    • Lactose, which is found in milk and other lactose containing products. If you’re lactose intolerant, it means you have either too little or no lactase, which is the enzyme which helps to digest milk sugar lactose.
    • Vaso-active amines, which are found in red wine, some cheeses, tuna, mackerel and some pork products.
    • Chemicals, which are naturally found in some foods, such as salicylate and glutamate and some food additives.

    If you’re intolerant to a food, the symptoms usually develop more slowly than with a food allergy. It can take hours or sometimes days for symptoms to appear and how severe these are usually depends on how much of the food you’ve eaten. Symptoms are usually related to your gut, such as diarrhoea, constipation and abdominal pain, as well as skin conditions such as eczema.

    If you think you may have a food intolerance, see your GP. You may need further tests and your GP may refer you to a dietitian for specialist advice.

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  • Reviewed by Graham Pembrey, Lead Editor, Bupa Health Content Team.
    Expert reviewer Dr Alexander Alexandroff, Consultant Dermatologist
    Next review due September 2021

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