Food allergy and intolerance
In this fact sheet: Symptoms, Gluten, Eggs, Nuts & seeds, Milk, Soya, Tests & diagnosis, Further information
Disclaimer: This information is not intended nor implied to be a substitute for professional medical advice. You assume full responsibility for how you choose to use this information. Always seek the advice of your doctor or other qualified healthcare provider before starting any new treatment or discontinuing an existing treatment. Talk with your healthcare provider about any questions you may have regarding a medical condition. Nothing contained here is intended to be used for medical diagnosis or treatment.
Food allergies, which involve a specific immune response, affect around 1 in 70 adults, and 8% children in the UK. Food intolerance affects many more people. Symptoms range from mild discomfort to severe or life-threatening reactions which require immediate medical attention.
Food allergies are more common in young children than in adults and many children outgrow food allergies. However, it is possible to develop a food allergy or intolerance as an adult.
Symptoms of food allergy or intolerance include:
- itching and/or swelling of lips, mouth, tongue and throat
- skin reactions - swelling and itching, eczema and facial flushing
- diarrhoea, feeling sick, vomiting and bloating
- coughing, wheezing or shortness of breath
- runny nose, sore, red and itchy eyes
- headache, migraine, sinus problems
Symptoms that affect your whole body include:
- extreme tiredness
These symptoms can be caused by problems other than food allergies, so you should visit your GP for advice. Automimmune conditions such as MS, Crohn's disease and rheumatoid arthritis usually involve some form of allergy or intolerance of certain foods. Coeliac disease is the most common condition involving gluten intolerance. Reactions are most common from proteins, such as gluten and egg, or sugars such as lactose in milk.
There are many foods that are known to be potentially allergenic, including:
- cereals containing gluten (including wheat, rye, barley and oats)
- mushrooms and QuornTM
- nuts (including brazil nuts, cashews, hazelnuts, almonds pinenuts and walnuts)
- peanuts (also called groundnuts or monkey nuts)
- sesame seeds
- soft fruit, strawberries
- sulphur dioxide or sulphites (preservatives in dried fruit, wines)
Gluten is a protein found in cereals such as wheat, rye and barley. Some people react to a similar protein found in oats.
Vegetarian foods suitable for people with gluten allergy or intolerance include eggs, cheese, milk, yoghurts, fruits, vegetables and pulses (peas, beans and lentils), and gluten-free grains.
Vegetarians obtain protein, minerals and B vitamins from grains so it is important to have a good mix of gluten-free grains, including breads and pasta. The Coeliac Society is an organisation with useful information for people living with coeliac disease and for those with gluten intolerance. View their Guide to Common Grains.
Gluten is found in many pre-packaged vegetarian foods such as veggieburgers and sausages, QuornTM products, soups and baked beans so always check the label.
Food products are subject to change and ingredients can be unexpectedly introduced into a product. Gluten food alerts and labelling advice is available from the Coeliac Society.
Egg allergy is most common in babies and young children under the age of one. About half of all children who are allergic to eggs will outgrow it by 3 years of age, and very few children still have an egg allergy after the age of six. Occasionally egg allergy can carry on into adult life, especially if you have eczema or other allergies. Reaction to eggs can cause a rash around the mouth in addition to symptoms listed above.
Always check the label carefully for egg products if you have an allergy.
Some people are able to eat cooked or well processed eggs without having a reaction because the proteins in the egg white are altered by heat. However, this is not the same for everyone. Egg allergies can also occur from birds other than hens.
For further help and information have a look at the British Egg Information Service and The Anaphylaxis Campaign.
Nuts and seeds
Nuts are one of the most common causes of food allergy. Nut allergies can occur at any age but it is most likely to happen before the age of three.The number of people in the UK who may be allergic to nuts is increasing. One report suggested a quarter of a million children (one in 50) in the UK are allergic to nuts.
Nut allergies tend to be to peanuts or tree nuts. Tree nuts include brazils, almonds, cashews, hazelnuts, walnuts and pecans. Peanuts, also known as groundnuts or monkey nuts, are actually legumes, related to peas and beans. If you have a peanut allergy, it is possible that you will be allergic to other legumes such as soya beans and green beans. People who are allergic to nuts are also commonly allergic to sesame seeds and sesame products like toasted sesame oil and tahini.
For support with nut allergies see www.anaphylaxis.org.uk
Cow's milk can cause reactions due to the sugar, lactose, and the presence of the proteins, such as casein. Milk allergy and lactose intolerance are often confused because they both occur after eating or drinking dairy products and they can cause similar symptoms.
Lactose intolerance is caused by the body's inability to break down lactose, due to a shortage of the enzyme, lactase, in the digestive system. Lactose intolerance affects older children and adults, whereas milk allergy is more common in babies and young children. It is important to determine which allergy you have because milk allergy can cause severe reactions. If you have lactose intolerance, undigested lactose can cause digestive problems, such as diarrhoea and bloating.
Milk allergy occurs when the body's immune system mistakes the proteins found in milk as harmful. Milk allergy occurs after having a small amount of milk, but people with lactose intolerance may be able to consume some dairy products without feeling ill. Although an allergic reaction to milk can cause similar symptoms to lactose intolerance, it can also cause allergic reactions, such as difficulty in breathing and hives (red, itchy swellings on your skin).
Milk allergies are more common in children, but most children outgrow them by the age of three. Adults rarely have a milk allergy but can be lactose intolerant.
In some cases goat or sheep's milk and dairy products can be tolerated but this must be done with the professional guidance of a GP or dietitian. If you think your child may be allergic to milk, talk to your doctor or health visitor before making any dietary changes.
A convenient replacement for dairy products for older children and adults is fortified soya, oat or rice milk, soya yoghurts and vegan cheese.
Soya allergy is not uncommon in children but many outgrow it by the age of two. Symptoms are similar to those of milk allergies - rashes, vomiting, stomach cramps and breathing difficulties. Tofu and soya milk are made from soybeans. Some fermented soy foods such as tempeh, shoyu and miso cause less allergy than whole soybeans, because the fermentation process partly breaks down the proteins. Soya oil is also regarded as unlikely to produce an allergic reaction.
Soya is found in a wide range of food products including bread, biscuits, cakes, pre-packaged meals and soups so check the labels carefully.
Tests and diagnosis
Elimination and challenge diets
An allergy specialist may ask you to remove the suspected allergy food from your diet and replace it with another food. If your symptoms improve, a diagnosis can usually be made. To confirm this diagnosis, your doctor may then ask you to re-introduce the food back into your diet. If you have had severe allergy symptoms in the past, this will be done under medical supervision in hospital.
It is important, particularly for children, that you don't cut out food groups without first seeking medical advice because you could risk reducing intake of essential nutrients.
Skin prick tests
An extract of the suspect food is put on a small patch of skin, usually on your forearm or back, and a very small, fine scratch is made. If redness and swelling develops around the scratch, the test is positive.
However, you can develop a positive reaction to this type of test without having allergic symptoms when you eat the food, so it is usually used in combination with other tests.
Blood tests are useful if you have a severe food allergy and are at risk of anaphylaxis, or if you have eczema or dermatitis and cannot have a skin test. The RAST (radioallergeosorbent) test measures levels of food-specific antibodies in the blood.
Symptoms of mild food allergies, such as a rash or runny nose, may be treated with antihistamines. However, it is important that you only take medicines for your allergy on the advice of your doctor.
The Food Standards Agency has produced a useful booklet which can be viewed on-line covering information and advice on all food allergies and intolerance.