Soy (soya) allergy: symptoms, label reading and what to avoid in the UK

A food allergy happens when the immune system overreacts to a particular food. The NHS says it is not clear why, but soybeans, along with milk, eggs, peanuts, tree nuts, shellfish and wheat, are among the most commonly allergic foods. You have a slightly higher chance of a food allergy if you or a close relative have other allergies, asthma or eczema.

Allergy UK explains that the soya bean belongs to the legume family, together with peas, beans, carob, liquorice and peanut. Soy comes from soybeans, immature soybeans are called edamame, and soya can be eaten as whole beans, flour, sauce or oil. A reaction to more than one legume is rare, so people with soya allergy usually do not have to avoid all legumes.

Soya allergy is different from food intolerance. The NHS says intolerance causes symptoms such as bloating and tummy pain usually a few hours after eating, while allergy involves the immune system and can cause serious reactions.

The NHS says symptoms of food allergy can affect any part of the body, sometimes several at once, and may start straight after eating or days later.

• Feeling dizzy or lightheaded.

• Itchy skin or a raised rash (hives).

• Swelling of the lips, face and eyes (angioedema).

• Coughing, wheezing, breathlessness, noisy breathing or a hoarse voice.

• Sneezing, or an itchy, runny or blocked nose.

• Feeling or being sick, tummy pain or diarrhoea.

The NHS says to call 999 if your lips, mouth, throat or tongue suddenly swell, you are breathing very fast or struggling to breathe, your throat feels tight or you cannot swallow, your skin, tongue or lips turn blue, grey or pale, you suddenly become very confused, drowsy or dizzy, someone faints and cannot be woken, or a child is limp, floppy or not responding as usual. If you have an adrenaline auto-injector or nasal spray, use it immediately and then call 999, even if you or the person feels better.

Allergy UK says the soya used in manufactured foods can be whole beans, soya flour, soya sauce or soya oil, and soya may also appear as a texturiser (textured vegetable protein), an emulsifier (soya lecithin) or a protein filler. It is found in breads, cakes, processed foods such as ready meals, burgers and sausages, and baby foods.

Allergy UK lists terms that may indicate soya, such as vegetable protein, textured vegetable protein, hydrolysed vegetable protein and hydrolysed plant proteins, and foods that contain soya such as tofu, tempeh, miso, edamame, soya milk, soya yoghurts and desserts, soya infant formula and teriyaki sauce. Products that may contain soya include bread, breakfast cereals, margarine, sausages, soups, sauces, ready meals and snack bars.

Allergy UK says soya is classed as a major food allergen and must be clearly identified on the ingredient labels of pre-packed foods, and that foods sold loose, such as at delicatessens and bakeries, have to provide ingredient information. It advises asking before buying or eating, and notes that foods sold elsewhere may not have to comply with the same laws.

It also advises caution with lists published by supermarkets and manufacturers, because they quickly go out of date and ingredients change. The NHS advice is to check food labels and restaurant menus carefully, tell staff at restaurants and cafes about your allergy, tell airlines before you fly, and not cut foods from your diet without speaking to a GP.

The NHS advises seeing a GP if you think you or your child may have a food allergy. You may be referred to a specialist for tests, which can include a skin prick test, blood tests and a supervised diet in which you avoid the food to see if symptoms improve. A food and symptoms diary can help identify triggers.

Treatment is avoidance of the foods you are allergic to, with antihistamines for mild reactions and adrenaline auto-injectors or a nasal spray for severe reactions, plus an allergy action plan from your specialist. Because avoidance levels differ, a dietitian can help ensure you eat a varied diet and avoid unnecessary restriction.

NHS allergy care starts with the GP and, where needed, a specialist or paediatric allergy service, with dietetic support available. Many people with soya allergy in childhood can be reviewed over time, and the NHS route provides this follow-up.

Private allergy clinics and dietitians can give faster appointments. Check their qualifications and avoid unvalidated tests, and share results with your GP so that your records and any emergency medicines are kept up to date.