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    What is Food Allergy?
    Our bodies are protected from infections by our immune system. We produce molecules, called antibodies, which recognise the germs causing an infection. There are a number of different sorts of antibody, and the one which causes an allergic reaction is called IgE. We think that IgE molecules are normally produced in response to infections caused by parasites, like those that cause malaria. We do not understand why, but some people make IgE to other things like pollen, giving rise to hay fever, and to some foods, giving rise to food allergies.

    The IgE acts like a tag, sticking to molecules in food or pollen called allergens. When someone who has an allergy eats a problem food the IgE attaches to the allergens, setting off an allergic reaction. One of the common effects that IgE triggers is the release of histamine, which causes the changes we see in our bodies as symptoms, like nettle rash or wheezing.

    Allergens are usually proteins, and there are generally several kinds of allergen in each food. We do not know what makes some proteins, and not others, food allergens.
     

    Allergy or Intolerance?
    There is another collection of symptoms that people report suffer from when they eat certain foods, such as headaches, muscle and joint aches and pains, and tiredness, which are often collectively known as food intolerance. This collection of symptoms is less well defined and poorly understood, and hence is generally much harder to diagnose than classical allergy.

    The exceptions are the gluten intolerance syndrome, known as Coeliac's disease, and lactose intolerance. Coeliac's disease is triggered by eating wheat, barley and rye-containing foods, whilst lactose (a sugar found in milk) can cause intolerance to milk in certain individuals who lack the ability to break it down. Lactose intolerance is not an allergy, but causes some of the same symptoms as milk allergy, like cramping pains in the stomach and diarrhoea.


     
    Symptoms of Food allergy
    Reactions to foods are usually rapid, appearing within an hour (or sometimes even seconds) of consumption, although in some cases they may be delayed and appear up to four hours after eating.
    • Skin rashes, such as nettle rash (also called urticaria or hives) can appear which are generally short lived, disappearing within a few days. Longer lasting, chronic skin reactions (such as scaly patches) can also be experienced. Some of these longer lasting rashes are called atopic dermatitis.
    • An itchy nose and eyes, sneezing and a runny nose may be experienced, as can asthmatic symptoms, such as wheezing, breathlessness and coughing. These types of symptom are not seen so often with food allergies.
    • Itching and swelling around the lips and mouth may occur on contact with a food. Other symptoms include nausea, cramping pains, bloating, vomiting and diarrhoea.

    .An uncommon allergic reaction, which can be life-threatening, is called anaphylaxis. It can be triggered by consuming very small amounts of food (just a bite is enough) and the symptoms usually appear within minutes and last for several hours. Asthma, skin rashes, nausea, vomiting and diarrhoea are among the symptoms which can be experienced. An unusual from of this condition can be triggered by eating problem foods within 2-3h of vigorous exercising and is called exercise-induced anaphylaxis. Prompt administration of adrenaline after eating suspected problem foods has helped minimise life-threatening episodes.


     
    Risk Indicator

    If you suspect you are having, or might have an anaphylactic attack, SEEK MEDICAL ASSISTANCE IMMEDIATELY. If you suffer an attack, and have no medication such as Epinephrine to hand, dial 999 immediately.


    Triggers
    There are a number of groups of foods that are responsible for causing the majority of food allergies. The list below gives some information on these allergens. The list of foods for which allergies have been reported is much longer. A more comprehensive list can be obtained from Food Allergy Network or visit the Anaphylaxis Campaign and view their list of food warnings. This carries info on all the latest warnings released by manufacturers (UK) about peanut and other accidental cross contamination

    Cow's Milk: Two out of a hundred infants under one year old suffer from cow's milk allergy, making it the most common food allergy of childhood. In general children lose this sensitivity as they grow up with nine out of ten losing it by the age of three; it is unusual for adults to suffer from this allergy.

    Symptoms are frequently vomiting and diarrhoea in children, with 30-50% also having skin rashes of some type. A small number of children have an anaphylactic reaction to milk which tends to be lifelong.

    The major allergens in milk are the caseins and the whey protein b -lactoglobulin. People are usually allergic to more than one kind of milk protein.

    The proteins from cow's milk are very similar to those from goats and sheep, and can cause the same sorts of reaction in cow's milk-allergic subjects. Thus goat's or sheep's milk cannot be used as a cow's milk substitute in allergic individuals.

    Eggs: Allergy to eggs is usually observed in young children rather than adults, and like cow's milk allergy, fades with time. Occasionally children suffer from a severe form of allergy which is not outgrown. The main allergens are the egg white proteins ovomucoid, ovalbumin, and ovotransferrin.

    The eggs of other poultry, such as ducks, are very similar to those of hens and can cause reactions in egg-allergic individuals.

    Fish and shellfish: Allergies to shellfish are unusual in children, mostly being experienced by adults. Reactions to fish are found in children and adults. The incidence of seafood allergy is higher in those countries with a high consumption of fish and shellfish.

    Severe reactions are more frequently found with these foods, including anaphylaxis. Cooking does not destroy the allergens in fish and shellfish, and some individuals maybe allergic to the cooked, but not raw, fish.

    The major allergens in fish are flesh proteins called parvalbumins which are very similar in all kinds of fish. This is why people allergic to cod tend to be allergic to fish such as hake, carp, pike, and whiting as well.

    Shellfish allergens are usually found in the flesh and are part of the muscle protein system, whilst in foods such as shrimps, allergens have also been found in the shells.

    Fruits: In general allergic reactions to fruits and vegetables are mild, and are often limited to the mouth, and are called the oral-allergy syndrome (OAS). Around four out of ten people having OAS are also allergic to tree and weed pollens. Thus people who are allergic to birch pollen are much more likely to be allergic to apples.

    There allergens in fruits and vegetables are not as complicated as other foods. Many of them are very like the allergens in pollens, which is why people with pollen allergies are also allergic to certain fruits. Many fruit allergens are destroyed by cooking, and thus cooked fruits are often safe for fruit allergic people to eat.

    Allergies to latex gloves, especially amongst health professionals, are increasing. As many of the latex allergens are like those found in certain tropical fruits, such as bananas, these people can get an allergic reaction to handling or eating these foods .

    Legumes: This group of foods includes soya beans and peanuts. Peanuts are one of most allergenic foods and frequently cause very severe reactions, including anaphylaxis.

    Allergy to peanuts is established in childhood and usually maintained throughout life. Both these foods have multiple allergens which are present in the raw and cooked foods.

    Peanut allergy can be so severe that only very tiny amounts of peanut can cause a reaction. Thus the traces of nuts found in processed oils, or the carry over of materials on utensils used for serving foods, can be enough in some individuals, to cause a reaction.

    The main allergens in peanuts and soya are the proteins used by the seed as a food store for it to grow into a seedling. One of the allergens in soya bean is very similar to a major allergen from dust mites, a common environmental allergen. We aren't sure yet whether this means there is a link between dust allergy and soya allergy.

    Tree nuts: This group includes true tree nuts, such as Brazil nuts, hazelnuts, walnut and pecan.

    Whilst not as intensively studied as peanuts, indications are that tree nuts can cause symptoms as severe which can occasionally be fatal. Children who become sensitised to tree nuts tend to remain allergic throughout life.

    Hazelnut and almond allergies are more like those people get to fruit, and are linked to pollen allergies. Nut allergens can be both destroyed by, or resistant, to cooking and we think that roasting may actually create new allergens.

    The allergens can be the seed storage proteins, or other molecules which are also found in pollen.

    Cereals: Suffered by children and adults alike, wheat allergy appears to be particularly associated with exercise-induced anaphylaxis.

    The more of a cereal (wheat, rye, barley, oats, maize or rice) we eat the more likely we are to suffer an allergy. Thus rice allergy is found more frequently in populations eating ethnic diets. Seed storage proteins (such as wheat gluten) and other proteins present in grain to protect it from attack by moulds and bacteria, have been found to be major allergens.


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    What helps?
    If a food allergy or intolerance is suspected then a visit to the GP is the place to start as he can refer you to an allergy specialist who can make a correct diagnosis (as detailed earlier). Once the diagnosis of food allergy has been made, avoidance of the causative food is essential. Occasionally complete elimination of the food for 1-2 years may result in a loss of clinical symptoms, but allergies to fish, peanuts usually persists for life.

    Complete avoidance of the offending food is often difficult due to the presence of very small quantities in commercially manufactured foods. Progress towards comprehensive labelling of food allergens has led to better management of allergies, but cases of malnutrition resulting from the mismanagement of diets due to fear and lack of knowledge have been reported. There is therefore a need for proper dietetic planning which should be given by a health professional with a specialised knowledge in this area (usually a dietician or nutritionist). Advice given would ensure that a diet is nutritionally adequate (with the use of nutritional supplements if necessary) with specific advice of what foods are likely to contain the offending foods. Sometimes food allergens are labelled using names that the consumer is not accustomed to. Education of the allergy patient is therefore vital, but it is not where food allergy management ends, in fact it is where it starts. Armed with knowledge the food allergic person can be constantly vigilant about what they eat, and they need to be!

    Where there is an indication that a food allergy may have been outgrown, an effort to safely introduce the offending food in the allergic individual's diet is done by a careful challenge procedure in a setting where any serious reactions can be properly managed (i.e. in hospital). It needs to be established whether the food is safe in all forms (e.g. raw and or cooked). Appropriate advice on what can be introduced into the diet needs to be given by an appropriately qualified individual.

    Food allergy -even when severe -can be managed perfectly well. What is required is sound medical guidance and a commitment by the patient to remain vigilant and always carry prescribed medication.

     

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    Medication

    The treatment for a serious allergic reaction is adrenaline (also known as epinephrine). During anaphylaxis, blood vessels leak, bronchial tissues swell and blood pressure drops, causing choking and collapse. Adrenaline (epinephrine) acts quickly to constrict blood vessels, relax smooth muscles in the lungs to improve breathing, stimulate the heartbeat and help to stop swelling around the face and lips (angioedema).
    Pre-loaded adrenaline injection kits are available on prescription for those believed to be at risk. These are available in two strengths - adult and junior. The injection must be given, as directed, as soon as a serious reaction is suspected and an ambulance must be called. If there is no improvement in 5-10 minutes, give a second injection.

    Because this must be administered without delay, patients known to be at risk often carry their own adrenaline injection kits for use in an emergency.

    The injection many doctors prescribe is the EpiPen, an easy-to-use device with a concealed needle. The EpiPen is available on prescription and distributed by ALK -Abelló, 2 Tealgate, Hungerford, Berkshire RG17 0YT. Tel 01488 686016.

    A relatively new adrenaline injection kit called the Anapen is also available on prescription. It is manufactured and distributed by Celltech Pharmaceuticals Ltd, 208 Bath Road, Slough, Berkshire SL1 3WE. Tel 01753 447690.

    Both companies provide trainer pens for practice purposes. For information on how to administer the EpiPen (click here) and Anapen, (click here).

    It is important to emphasise that even after adrenaline is administered, medical assistance should be sought urgently because the effects may wear off after 5 to 10 minutes and the injection may have to be repeated.

    In fact, doctors often prescribe more than one injection kit so that if medical assistance is delayed, patients may administer a second dose.


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    Statistics
    It is a sad fact that there are very few statistics available on Anaphylaxis related deaths in the UK. This makes it very difficult to gauge with any level of certainty, the effectiveness of treatments such as Epinephrine, or to evaluate how many individuals who are diagnosed as suffering from anaphylaxis suffer fatal attacks.

    More than one child in 100 is believed to suffer severe allergic reactions to peanuts, tree nuts or both. A small but significant number are affected by other foods.


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