Most Common food allergens

Any food can cause an allergy, theoretically. However, just a handful of foods cause at least 90% of allergic reactions to food.

The substance that causes an allergic reaction in foods or drinks is called an "allergen". As far as foods are concerned, nearly all allergens are proteins. For the majority of people these proteins are not allergens, because their immune system does not react to them.

The most common allergenic foods, also known as the 'big eight', are:
*eggs
*fish
*milk
*nuts from trees (including hazelnuts, walnuts, almonds, and Brazil nuts)
*peanuts (groundnuts)
*shellfish (including shrimps, mussels, and crab)
*soya
*wheat
Among children, most allergic reactions to food are to peanuts, milk, soya, nuts from trees, eggs and wheat. The majority of children stop being allergic to foods early on in their childhood. Allergic adults typically react to citrus fruit, nuts, fish, peanuts, shellfish and wheat. Pesticides in tap water causing more food allergies Researchers from the American College of Allergy, Asthma and Immunology found that pesticides in tap water could be causing the recent rise in food allergies. They published their study in the December 2013 issue of Annals of Allergy, Asthma and Immunology.

The scientists explained that chemicals used to chlorinate water as well being added to pesticides dichlorophenols are associated with food allergies when found in a person's body.

What is the difference between food intolerance and a food allergyA food allergy triggers an immune system reaction that affects several organs in the body. Food intolerance symptoms are less severe and affect only the digestive system. In fact, experts say that many people who believe they have a food allergy have some kind of food intolerance.

Cereal allergy Cereal allergies can affect both children and adults. The most common foods in this category are oats, wheat, maize (corn), rice, rye and barley.

Some patients may be allergic to more than one type of cereal. Coconut allergy Coconut allergy is uncommon. Affected patients can have serious reactions, including anaphylaxis, which can be dangerous.

People with nut allergies and/or latex allergies are more likely to be allergic to coconut. Coeliac disease Gluten can be found in barley, rye, wheat oats and some other cereals. It consists of a mixture of proteins.

Celiac disease (gluten intolerance) is a chronic disease, which can eventually damage the lining of the small intestine, affecting the bodys ability to properly absorb nutrients, causing diarrhea and eventually malnutrition. Celiac disease may be hereditary, it can sometimes run in families, but experts are not sure what causes it. 

The Food Standards Agency, UK, has estimated that possibly 1 in every 300 UK citizens is affected with celiac disease. In Ireland, as many as 1 in 100 people may be affected.

If a person has celiac disease, they will typically be diagnosed as infants after weaning, when cereals are added t their diet. However, the disease can emerge later on in life. Some studies have found that holding back on wheat foods until the baby is at least four to six months old may reduce the risk of developing celiac disease.

Untreated celiac disease can lead to bone disease, anemia, and even certain types of cancer (very rarely). Some children may have growth problems.

Celiac disease is also more common among patients with certain neurological disorders, ulcerative colitis, type 1 diabetes, and thyroid problems.

Celiac disease is incurable. Avoiding symptoms is simply a question of gluten-containing foods, including beer and lager, malt flavoring, malt extract, malt, barley, rye, oats and wheat.

Processed foods commonly contain hidden gluten. However, a large number of gluten-free products, such as pasta, cakes and bread are available in some bakeries, specialist shops and supermarkets. Coeliac UK, a charity to support people with gluten intolerance, works with manufacturers to produce a regularly updated list of foods that don't contain gluten. Read more about celiac disease. Egg allergy Like most food allergies, egg allergy is more common in childhood and about half the children who have it will grow out of it by the age of three. In a few cases, egg allergy can cause anaphylaxis. 

Egg allergy is mainly caused by three proteins in the egg white called ovomucoid, ovalbumin and conalbumin. Cooking can destroy some of these allergens, but not others. So some people might react to cooked eggs, as well as raw eggs. 

Occasionally someone might react to egg because they have an allergy to chicken, quail or turkey meat, or to bird feathers. This is called bird-egg syndrome. Fish allergy Fish allergy can often cause severe reactions, including anaphylaxis. Adults are more likely to have an allergic reaction to fish and shellfish than children, which is probably because adults will have eaten these foods more often. 

People who are allergic to one type of fish, such as cod, often react to other types of fish such as hake, haddock, mackerel and whiting as well. This is because the allergens in these fish are quite similar. Cooking doesn't destroy fish allergens. In fact, some people with fish allergy can be allergic to cooked but not raw fish. Fruit and vegetable allergy Allergic reactions to fruits and vegetables are usually mild and often they just affect the mouth, causing itching or a rash where the food touches the lips and mouth. This is called oral allergy syndrome. A number of people who react in this way to fruit or vegetables will also react to tree and weed pollens. So, for example, people who are allergic to birch pollen are also likely to be allergic to apples. 

Cooking can destroy a number of the allergens in fruits and vegetables, so cooked fruit often won't cause a reaction in people with an allergy to fruit. Pasteurised fruit juice might not cause an allergic reaction either, for the same reason. However, the allergens in some vegetables, such as celery, aren't affected by cooking. Some fruits and vegetables, such as tomatoes, are more likely to cause a reaction as they get riper.

Latex-food syndrome Latex allergy is caused by a reaction to a number of allergens found in natural rubber or latex. In recent years, the number of people with latex allergy has increased, particularly among healthcare workers and people with spina bifida, because they come into contact with lots of latex products. 

Latex contains lots of allergens that are similar to the allergens in some foods. So people who are allergic to latex might also find they react to foods such as banana, mango, kiwi, chestnut, paprika, celery, apple, carrot, cherry, coconut, strawberry and avocado. This is called latex-food syndrome. In the same way, people who are allergic to these foods may also react to latex. 

People with a latex allergy should be tested for allergies to foods that are linked to the latex-food syndrome. Lupin allergy Lupins are common garden plants, which are related to legumes such as peas, lentils and beans. Many types of lupin seed are poisonous, because they contain bitter-tasting toxins. But sweet lupins don't contain these toxins and they can be eaten by humans or livestock. Sweet lupin seeds are being used more and more to replace cereal grain in many food products, for example flour and pasta. 

Allergy to lupin has been recognised for some time in mainland Europe, where lupin flour is used widely in food products. This type of allergy only seems to have started emerging in the UK quite recently, which is probably because lupin is used quite rarely in food products and hasn't been used for as long as in mainland Europe. Lupin allergy can cause severe reactions, including anaphylaxis, but there have been very few confirmed reports of lupin allergy in the UK so far. 

The major allergens in lupin are also found in peanut, so people who are allergic to peanuts could react to lupin. The Anaphylaxis Campaign in the UK has advised people with peanut allergy to avoid lupin. It's mainly used in flour-based products such as pastry. Maize allergy Maize (or corn) allergy isn't common in the UK, although there have been reported cases. For people who are sensitive to maize, avoiding it can be very difficult, because maize is commonly used in a wide variety of food products. Meat allergy People with a meat allergy might react to beef, mutton, pork or chicken. Sometimes people who are allergic to one type of meat or poultry might also react to other types. Cooking destroys some of the allergens in meat, but some people will still react to cooked meat. 

Processed meats, such as frankfurters, luncheon meats and pates, sometimes contain other ingredients, particularly milk products, as emulsifiers or flavour enhancers. So it's possible for someone who is allergic to milk to react to a meat product because it contains milk. For example, milk is sometimes used in chicken nuggets to stick the breadcrumbs to the chicken pieces. Milk allergy Allergy to cows' milk is the most common food allergy in childhood, and affects 2-7% of babies under one year old. It's more common in babies with atopic dermatitis. A reaction can be triggered by small amounts of milk, either passed to the baby through the mother's breast milk from dairy products she has eaten, or from feeding cows' milk to the baby. 

Children usually grow out of milk allergy by the age of three, but about a fifth of children who have an allergy to cows' milk will still be allergic to it as adults. The symptoms of milk allergy are often mild and can affect any part of the body. They can include rashes, diarrhoea, vomiting, stomach cramps and difficulty in breathing. In a very few cases, milk allergy can cause anaphylaxis. 

Cows' milk allergy is caused by a reaction to a number of allergens in cows' milk, such as casein and a whey protein called beta-lactoglobulin (BLG). New Zealand scientists genetically modified a cow which now produces milk that is low in BLG. Casein is the curd that forms when milk sours, and whey is the watery part that is left when the curd is removed. 

People can be allergic to either whey or casein, or both, and an allergic reaction can be triggered by very small amounts of these allergens in people who are sensitive. Heat treatment, such as pasteurisation, changes whey, so people who are sensitive to whey might not react to pasteurised milk. But heat treatment doesn't affect casein, so someone who is allergic to casein will probably react to all types of milk and milk products. 

Milk from other mammals (such as goats and sheep), and hydrolysed milk and soya formulas, are sometimes used as a substitute for babies who are at risk of developing cows' milk allergy. However, the allergens in milk from goats and sheep are very similar to those in cows' milk. This means that someone with a cows' milk allergy might react to these other types of milk as well, so goat's and sheep milk aren't suitable alternatives for people who are sensitive to cows' milk. 

Some highly hydrolysed milk formulas are suitable for babies with cows' milk allergy, but other types of formula, such as partially hydrolysed milk and soya formulas, aren't suitable, because many babies with cows' milk allergy might react to them as well. Milk protein intolerance Intolerance to cows' milk protein is a type of intolerance that is common in babies and children, and symptoms start from the time when cows' milk is first introduced into the diet. There is no cure for it and the only way to stop the symptoms is to avoid cows' milk products. Cows' milk protein intolerance is different to lactose intolerance and milk allergy. See the sections on lactose intolerance and milk allergy for more information. Nut allergy Allergy to nuts from trees is usually lifelong. The nuts that are most likely to cause allergic reactions are walnuts, hazelnuts, almonds, pecans, Brazil nuts, pine nuts, macadamia nuts and cashew nuts. On rare occasions, all these nuts can cause anaphylaxis in people who are sensitive. Sometimes people with an allergy to one type of nut will also react to other nuts. So if you have a nut allergy, you need to be very careful to avoid nuts and unrefined (crude) nut oil. Talk to your GP for advice. 

Strictly speaking, peanuts are legumes, not nuts, and they grow underground rather than on trees. See the section on peanut allergy. Peanut allergy Allergy to peanuts (also known as groundnuts and monkey nuts) is often lifelong, but research suggests that, in a very few cases, young children diagnosed with peanut allergy may grow out of it. 

Peanuts are one of the most common causes of food allergy and can cause severe reactions, including anaphylaxis. They contain a number of allergens that are not destroyed by cooking or roasting. 

Peanut allergy can be so severe that very tiny amounts can cause a reaction. Because of this, coming into contact with traces of peanut can be enough to cause a reaction in people who are sensitive. For example, someone might come into contact with traces of peanuts from unrefined oils, or when food is served using utensils that have been used with food containing peanuts, or even being close to someone eating peanuts. 

Refined peanut oil is thought to be safe for people with peanut allergy, because the proteins that cause allergic reactions are removed during the manufacturing process. However, cold-pressed, or unrefined/unprocessed (crude) peanut oil can contain small amounts of peanut allergens, which can cause a reaction in people who are sensitive. 

Some people with peanut allergy might also react to other legumes such as soya, green beans, kidney beans, green peas and lupins, because these foods contain similar allergens to peanuts. Even though, strictly speaking, peanuts aren't nuts, people with peanut allergy are sometimes allergic to nuts from trees such as almonds, walnuts, hazelnuts, Brazil nuts and cashew nuts. Pine nut allergy Pine nuts can cause severe allergic reactions, including anaphylaxis, in people who are sensitive. People who are allergic to pine nuts might also react to peanuts and nuts such as almonds. Quorn allergy Quorn is a type of protein, which is made from a fungus. It has been available in the UK since 1985, and is often used as a meat substitute. There have been some reports of intolerance to Quorn, but this is not surprising, because it has a high protein content (allergens are usually proteins). Intolerance to Quorn is much less frequent than to other foods such as soya and dairy products. As Quorn is made from a fungus, some people who react to other fungi or moulds (including by inhalation) may also react to Quorn. Rice allergy Rice allergy is common in countries in Eastern Asia, such as Japan, where rice is commonly eaten, but it isn't common in the UK. People who are allergic to rice can react when they eat it or when they inhale its pollen. Rice can cause hayfever symptoms in areas where it's grown commercially. 

People who are allergic to rice can sometimes react to a number of other foods from the same botanical family, such as barley, maize, wheat, oats and rye, as well as other foods such as peach and apple. Sesame allergy We don't know how many people in the UK suffer from sesame allergy, but it's quite common in countries such as Australia and Israel. We think that sesame allergy is increasing, possibly because it's now more commonly used. 

Sesame seeds, sesame oil and other sesame products such as tahini, are used in cooking, for example in Turkish or oriental dishes, and in manufactured products such as bread, biscuits, salads, sauces and houmous. Sesame allergy can be severe, and can cause anaphylaxis. People with sesame allergy might also react to poppy seeds, kiwi fruit, hazelnuts and rye grain. 

People who are allergic to sesame should avoid sesame oil. This is because it's made by cold-pressing sesame seeds and isn't refined, so it can contain small amounts of allergens, which can cause a reaction in people who are sensitive to them. Shellfish allergy Allergy to shellfish is quite common, and a number of different types of shellfish can cause reactions in people who are sensitive, for example shrimps, prawns, lobster, crab, crayfish, oysters, scallops, mussels and clams. 

People who are allergic to one type of shellfish often find that they react to other types. Shellfish allergy can often cause severe reactions, and some people can react to the vapours from cooking shellfish. Soya allergy Soya allergy is a common childhood allergy. Most people grow out of it by the age of two, but occasionally adults are allergic to soya. The symptoms of soya allergy are similar to milk allergy, and they include rashes, diarrhoea, vomiting, stomach cramps and breathing difficulties. Some people with soya allergy might also react to milk. Very rarely, soya can cause anaphylaxis. 

Soya is used as an ingredient in about two-thirds of all manufactured food products, including bakery goods, sweets, drinks, breakfast cereals, ice cream, margarine, pasta, processed meats and seasoned foods. 

Soya can be described in a number of different ways on food labels, for example as hydrolysed vegetable protein, vegetable oil and lecithin. Soya flour is used to increase the shelf life of many products and to improve the colour of pastry crusts. Textured soya protein, which is sometimes called textured vegetable protein, is made from compressed soya flour. It's used as a meat substitute and to improve the consistency of meat products. 

Refined soya oil (the main component of vegetable oil) should be safe for people with soya allergy, because the proteins that cause allergic reactions are removed during the refining process. 

Children who are allergic to cows' milk are sometimes given soya-based formulas as a substitute. But people with a cows' milk allergy can sometimes be allergic to soya too. So soya-based formulas might not be suitable for children with cows' milk allergy. Highly hydrolysed milk or casein formulas are often recommended for these children. Ask your GP for advice. 

Sometimes people with an allergy to soya will also react to foods such as peanuts, green peas, chickpeas, rye and barley flour. Spice allergy Allergic reactions to spices are rare and usually mild, but severe reactions can happen occasionally. Some people react to mustard, coriander, caraway, fennel, paprika or saffron and, less frequently, to onions, garlic or chives. Reactions to mustard have been reported to cause anaphylaxis, particularly in mainland Europe, where mustard is used more. The allergens in spices are similar to those in pollens and vegetables, and people who are allergic to mugwort and birch are more likely to be sensitive to spices for this reason. Vegetable oil allergy Vegetable oil is usually a blend of oils. In the UK, the oils used the most to make up vegetable oil are soya, rapeseed, sunflower, maize, palm, coconut and palm kernel oils. Where they appear in pre-packed food, these oils will have been refined. The refining process removes proteins from the oil. Since it's the proteins in oils that can cause allergic reactions, sensitive people probably won't react to refined oils. Some speciality oils, such as sesame and walnut, aren't refined, so they are best avoided by people who are sensitive to the nuts or seeds they are made from. Wheat allergyWheat allergy is common, particularly among babies. One of the main allergens in wheat is a protein called gliadin, which is found in gluten. Because of this, people with a wheat allergy are sometimes recommended to eat a gluten-free diet. 

As with all food allergies, if you think you're allergic to wheat you should talk to your GP before changing your diet Food allergies driving many children to over-restrictive dietsToo many children, especially those with eczema, are avoiding foods unnecessarily based on poor data about potential food allergies, researchers at National Jewish health reported in The Journal of Pediatrics (October 2010 issue).

avoiding too many foods increases the risk of malnutrition. Basing which foods to eat primarily on data from serum immunoassays (blood tests) is not recommended, they added.

When evaluating food allergies, the following factors should be taken into account:

patient medical history

family history

blood tests

skin tests

The Oral Food Challenge is the gold standard test (patients consume suspected allergenic foods)