Food allergy

Expert reviewer Dr Michael Ardern-Jones, Consultant Dermatologist
Next review due February 2019

A food allergy is when your body’s immune system overreacts to particular foods, for example, eggs or nuts. If you have a food allergy, it may cause symptoms such as a rash, swollen lips, stomach ache, itching and sneezing.

Healthy smmothie and bananas

About food allergies

If you have a food allergy, your body’s immune system reacts to a particular protein in a certain food and tries to fight it. Most people with a food allergy only get a mild reaction, but for others they can be life-threatening and need emergency treatment.

Food allergies are more common in children than in adults, because some people lose their food allergy as they grow up. Although most people with a food allergy develop it as a child, it’s possible to develop one at any age. About a third of children with a food allergy are allergic to more than one type of food.

Common foods people are allergic to

  • Peanuts and tree nuts. These include almonds, cashews, macadamia nuts and Brazil nuts, and are the most common cause of a food allergy. Although children often outgrow some food allergies, four out of five children with a nut allergy will still have the allergy when they’re an adult.
  • Cow’s milk. An allergy to cow’s milk is more common in children than in adults. Infants usually show an allergic reaction in their first few months, but most children grow out of their allergy by the age of five.
  • Eggs. An allergy to eggs is more common in children than in adults. Some children with an egg allergy can eat well-cooked egg, but not raw or loosely cooked egg. Most children grow out of their egg allergy.

Other foods that people can be allergic to include:

  • seeds, such as sesame seeds
  • shellfish
  • fish
  • wheat
  • soya
  • kiwi fruit

Symptoms of food allergy

An infographic showing the symptoms of food allergy

These symptoms could also be caused by other conditions and illnesses. See your GP if you have any symptoms that concern you.

Diagnosis of food allergy

Your GP will ask you questions about your allergic reaction, such as how quickly it develops, how severe it is and the possible cause.

If your GP thinks you may have a food allergy, they might carry out some simple tests, such as a blood test. Or, they may refer you to a specialist allergy clinic for tests. Common allergy tests are listed below.

  • Skin tests. A weak liquid containing the suspected cause of your allergy is put on your skin and a small needle prick is made through it. After 15 to 25 minutes, you’re likely to get a small reaction around the needle prick if you’re allergic to the food tested.
  • Blood tests. These measure the amount of antibodies in your blood to different food proteins. The antibodies are known as immunoglobulin E (IgE).
  • Elimination diets. 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 may be advised to start eating the suspected food again to see if your symptoms come back. If they do, it’s likely that you’re allergic to that food.
  • Food challenges. You’ll be given a small amount of food to eat to see if you have a reaction to it. This test should always be done with a specialist, so you can be safely treated if needed.

Other tests for food allergies, such as applied kinesiology, hair analysis and vega testing are not validated and not recommended for diagnosing food allergies.

A food allergy is sometimes confused with food intolerance. An intolerance can make you feel ill but isn’t usually as severe or potentially harmful in the same way that a food allergy can be. See our information on the difference between food allergy and food intolerance further down the page.

Treatment of food allergy

The only way to avoid having allergic reactions in the future is to carefully avoid all foods that trigger your food allergy. You may find that after avoiding the food for a year or two, your allergy disappears. For advice on avoiding trigger foods, see our information about living with a food allergy, further down the page.

If your symptoms are quite mild, your doctor may advise that you can take antihistamines if you get an allergic reaction. It might not be safe to rely only on these medicines if you have more severe symptoms though.


You may have heard of a treatment called immunotherapy. This involves being given regular, very small amounts of the protein that you’re allergic to, by injection or by mouth. Over time, the dose is increased so your body learns to accept the allergen.

This treatment is currently primarily used for some people with severe hay fever or allergies to wasp/bee stings or animals. Immunotherapy is being researched for food allergies too – a few studies show that it may work for some people. It’s not a standard treatment for food allergies yet though. More research is needed to check it works long term and that it’s safe. Never try this approach yourself at home, as it’s likely to cause an allergic reaction.

Emergency treatment for food allergy

If you’re at risk of having a severe allergy, your doctor or specialist may prescribe you an EpiPen®. This is adrenaline (epinephrine), which you can inject, and you should carry it with you at all times. This is just in case you accidentally eat or touch the food that you’re allergic to and have a bad reaction. An adrenaline injection works quickly by:

  • correcting low blood pressure by counteracting changes to your blood vessels
  • relaxing your airways, which helps you to breathe more easily
  • getting rid of any itching, swelling or hives

If you’re likely to have a severe reaction to a food, your doctor or specialist may suggest that you wear a medical emergency identification bracelet. This is so that people can understand what’s happening and can get you the help you need quickly.

If you have a severe allergic reaction and are having problems breathing, get someone to call 999 for an ambulance immediately. If you have an EpiPen® or other injectable adrenaline, use it as you’ve been instructed but still seek emergency medical attention.

At hospital, you may be given adrenaline to help treat your symptoms. You might also be given oxygen or have a drip attached, so that you can be given fluids into your bloodstream. If your condition gets worse, you may need to be connected to a machine that helps you breathe until your allergic reaction eases.

Causes of food allergy

Your immune system’s job is to protect your body from harmful molecules and infections. Many food allergies develop when your body makes a type of antibody called immunoglobulin E (IgE) in response to a specific protein in a food. Your body does this because it thinks the protein is harmful. The next time you eat or touch that food, the immunoglobulin in your body will trigger alarm signals. These tell your immune system to fight the protein it thinks is harmful. This causes your body to release chemicals, which leads to the symptoms of your allergy.

If your food allergy is caused by your body having an IgE against that food, you’ll probably get an allergic reaction within minutes. However, sometimes, a food allergy is not caused by IgE. Instead, this type of allergy is known as T-cell mediated and is caused by immune cells reacting to the food proteins. If you have this type of food allergy, the allergic reaction may take hours or days to come on. Symptoms can include eczema, diarrhoea or constipation.

Some people are allergic to more than one food type, or have other allergies too. For example, if you have an allergy to latex, you might also be allergic to certain fruits including kiwis. This is called cross-reactivity.

The exact reasons why some people have food allergies and others don’t aren’t fully understood. Experts think that a number of things may cause food allergies, such as your genes and the environment you live in.

If you have asthma, eczema or hay fever in the family, you’re more likely to have a food allergy. The likelihood is also increased if another member of your family has a food allergy.

Complications of food allergy

The most severe complication of food allergies is anaphylaxis. This is a severe, full-body allergic reaction which can be life-threatening. If you don’t receive treatment quickly for severe anaphylaxis, it can be fatal. If you think you or someone else is having an anaphylactic reaction, call 999 for an ambulance and administer adrenaline if it’s available.

A severe reaction like this isn’t common. Only about 10 people in the UK die each year from a food allergy.

Another complication of food allergy is that if you have to cut a lot of foods from your diet, it may result in nutritional deficiencies. In the case of children, this can affect their growth. Before excluding food types from your child’s diet, it’s important to get expert advice. Your doctor may refer you to an allergy service where diets can be introduced under the guidance of a dietician.

Living with a food allergy

If you have a food allergy, you’ll need to avoid the foods you’re allergic to. Or, if your child has a food allergy, you’ll need to make sure they don’t eat those foods. The following tips may help.

  • Check the labels on foods carefully to find out whether they contain the ingredient you’re allergic to. You can now do this for unpackaged food, as well as ones in packets. The European Union has provided guidance that all businesses selling foods must label the 14 most common ingredients that can cause allergies (food allergens). This applies to restaurants, cafes and canteens, for example.
  • Be aware – labels warning that a food ‘may contain’ an allergen are not a requirement, so might not always be present.
  • If even very tiny amounts (trace amounts) of a food could give you an allergic reaction, be very careful to avoid any possible cross-contamination. Take extra care when you’re cooking at home, to make sure you don’t contaminate what you’re preparing with any foods that you’re allergic to. This may mean keeping certain foods, utensils and chopping boards separate and always cleaning them straight away.
  • Take extra care when you’re eating foods that haven’t been prepared or bought by you, such as at barbecues, buffets and parties. Let your friends know ahead of time about your allergies. Take your own snacks, in case there’s not a safe alternative for you.
  • Decide which areas of your kitchen will be kept ‘allergen-free’. For example, designate certain areas of your fridge, cupboards and work surface as places where you can or cannot put certain foods.
  • If you’re cutting out a food, such as cow’s milk, try to replace it with an alternative source of protein and calcium, eg, soya milk.
  • If you have medicines to take in case you have an allergic reaction, always remember to take them with you if you eat out.
  • 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 have a food allergy, you may want to ask your GP or allergy specialist to refer you to a dietitian. Your dietitian can explain how to identify problem foods and how to make sure you have a healthy, balanced diet without them.

Frequently asked questions

  • There are no proven ways to reduce the chances of your child developing a food allergy.

    More information

    Some women consider changing their diet during pregnancy or when breastfeeding to try and prevent a food allergy affecting their child. But there’s not enough proof that this works.

    Breastfeeding your baby might help to reduce the chance of them becoming allergic to cow’s milk, getting eczema or wheezing. There’s no proof that breastfeeding can prevent other food allergies, but it does have many other benefits for you and your baby.

    There is also no proof that using probiotics or prebiotics (which contain helpful bacteria or help these bacteria to grow) can prevent a food allergy.

    You might want to introduce your child to new foods that can cause allergies (like cow’s milk, peanuts and eggs) at different times. This is so that if your child does have a reaction, the cause is clearer.

  • Food allergies and food poisoning can often have very similar symptoms, so it might be difficult to tell which is causing your symptoms. If you’re concerned, speak to your GP.

    More information

    Diarrhoea, feeling sick, vomiting and abdominal (tummy) discomfort can all be symptoms of both food allergy and food poisoning. But there are some symptoms which you may get from food poisoning but not in food allergy and vice versa. Also, food poisoning will develop as a short, one-off illness, while food allergies tend to cause similar symptoms each time the food is eaten.

    The common symptoms of food poisoning include:

    • diarrhoea
    • feeling sick
    • vomiting
    • abdominal (tummy) cramps
    • a fever

    Food allergy can also cause diarrhoea, feeling sick, vomiting and bloating. You might get other symptoms with food allergy including:

    • coughing and wheezing
    • a runny nose
    • itchy or swollen lips, mouth, tongue and throat
    • skin reactions, such as a rash or hives

    These symptoms may also be caused by problems other than a food allergy or food poisoning. If you’re concerned about the cause of your symptoms, see your GP.

  • Some people with a peanut allergy might have a reaction on a plane if nuts are eaten by other passengers. The reaction is not usually severe, and there are some precautions you can take.

    More information

    Some people with a peanut allergy say that when they travel by aeroplane they sometimes have an allergic reaction during the flight. This may be because of peanut snacks that are served. Traces of peanut may be left on surfaces where people have previously eaten peanuts. Peanut dust may also spread in the air – although this is less likely. If you have a reaction to traces of peanut on an aircraft, it’s likely to only be mild or moderate.

    The meals served on aeroplanes may also contain, or be contaminated with, foods that could cause an allergy.

    If you have a severe peanut allergy and are concerned about flying, here are some tips to help.

    • Speak with your allergy specialist to get advice on your risk and the precautions you should take.
    • When you book your ticket, tell the airline that you have a severe peanut allergy and ask for a special meal. Double check that this has been arranged when you check in and when you board the plane.
    • Consider taking your own food on the plane rather than eating the airline food.
    • Some airlines don’t serve peanut snacks, and some will remove them from a flight if you ask well in advance. Ask your airline if they would consider this. Remember, they can’t stop people taking their own peanut snacks on board though.
    • Tell the cabin staff that you have a severe peanut allergy when you board the plane.
    • Clean your seat tray and area with wet wipes, and don’t use airline blankets or pillows.
    • Take any medicines you have been prescribed on the plane with you (such as antihistamines or an adrenaline injector). However, don’t take antihistamines as a precaution – they could mask your symptoms and mean that you don’t realise you’re having an allergic reaction.
    • Get a letter from your GP explaining why your adrenaline injector needs to be in your hand luggage.
  • Yes, if you have a peanut allergy, you might also react to lupins or products that contain lupin flour or seeds. 

    More information

    Lupin plants and peanut plants are both a type of legume (bean). If you’re allergic to peanuts, you may be allergic to lupins too. Lupin seeds can be ground to produce flour. Lupin flour isn’t used very often in foods made in the UK. It’s more commonly found in foods such as pastries and pasta, from other areas of Europe. Lupin flour is also used as a substitute for wheat flour in some gluten-free products. Some people can have severe reactions to lupin. So, if you’re allergic to peanuts it’s important to check food labels for lupin too.

    By law, all pre-packed food produced in the UK and the European Union must say on the label if it contains lupin.

  • If you have a peanut allergy, you’re unlikely to have an allergic reaction to refined peanut oil, but you could react to unrefined peanut oil.

    More information

    The part of peanuts that people are allergic to is the protein. However, peanut oil contains fat, not protein.

    If you have a peanut allergy, you’re very unlikely to react to refined peanut oil (arachis oil or groundnut oil). However, the safest option would be to avoid these products altogether, to reduce your risk of a reaction.

  • Both the yellow fever vaccine and some types of flu vaccine are prepared using egg protein. If you have an egg allergy, you should get advice from your allergy specialist before having either vaccination.

    More information

    The yellow fever vaccine is made using egg, and so if you are allergic to eggs, you could react to this vaccine. Some influenza (flu) vaccines are also prepared using eggs, but others are egg-free or have extremely low amounts of egg in them. It’s safe for people with an egg allergy to have some types of flu vaccine. Always get advice from your allergy specialist or your GP about having a yellow fever or flu vaccination.

    The vaccine against measles, mumps and rubella (MRR), doesn’t contain egg. If your child is allergic to eggs, it’s safe for them to have the MMR vaccination.

  • No, having food intolerance is different from having a food allergy. Food allergy symptoms are caused by your immune system’s reaction to a food. Food intolerance reactions don’t involve immunoglobulin E antibodies or your immune system. Because of this, they are often harder to diagnose.

    More information

    Food intolerances aren’t life threatening, but they can make you feel very unwell and have a major impact on both your physical and mental health.

    Reactions to food intolerance are often delayed, and can occur several hours or even days after eating something. Symptoms are usually related to your gut, such as bloating, diarrhoea and constipation, skin conditions, such as eczema, and joint pain. However, symptoms can sometimes be vague, and therefore food intolerances can be hard to diagnose.

    Apart from lactose intolerance, which can be diagnosed by your GP, there are no tests to diagnose food intolerances. Be sure to see your GP though. They may refer you to a dietitian. Keep a food diary and record labels of food you think are triggering your symptoms. Some food triggers will be obvious, while others may be harder to pinpoint. The more information your GP or dietitian has about your eating habits, the easier it will be for them to help you eliminate foods that may be causing you problems.

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  • Produced by Alice Rossiter, Specialist Health Editor, Bupa Health Content Team, February 2016
    Expert reviewer Dr Michael Ardern-Jones, Consultant Dermatologist
    Next review due February 2019

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