Soy allergy is a reaction to the proteins found in soybeans. Soyabean is a member of the bean family native to East Asia. In the UK it is seen most frequently in infants and preschool children, with about 4 in 1000 children thought to have the allergy.
About half of children with soy allergy have symptoms that begin immediately after eating food containing soya. Most symptoms are mild and may include a rash (hives or “nettle” rash), swelling of the lips or around the eyes, and itch. Some children have an itchy throat, others feel sick, vomit or have diarrhoea.
Severe reactions are much less common, but include difficulty breathing (with wheeze or swelling that blocks the mouth or throat), feeling faint or dizzy (anaphylaxis).
Sometimes symptoms are delayed. Common complaints are flares in the child’s eczema, colic or belly ache.
Most children with soya allergy only have mild reactions. Severe reactions affecting the child’s breathing can occur, particularly in those with bad asthma and these need urgent medical attention.
One in ten children with a milk allergy are also allergic to soya. This may become apparent when soya milk is tried as an alternative following the child’s reaction to dairy products.
Other legumes such as beans, pulses, lentils and chickpeas are usually tolerated. If you have any concerns, discuss them with your doctor or dietitian.
The diagnosis of soya allergy is based on the history of a typical reaction after contact with soya.
Positive allergy tests skin prick or blood IgE tests support the diagnosis, but should not be used alone, as many people can have a positive allergy test but tolerate the soya without getting a reaction. Skin prick tests are safe. They are done in clinic provided that the child has not had any antihistamines for a few days. Blood tests are not affected by antihistamines, but the results are only available a week or so after the clinic appointment. If the diagnosis is uncertain an oral soya challenge is recommended.
Soya is a popular vegetarian alternative to meat and many processed foods contain soya. It is also an ingredient in lots of cow’s milk and lactose free recipes. You should read the ingredients list on pre-packaged foods.
Soya can be avoided by looking for words like soy, miso, tempeh, tofu, bean curd and hydrolysed or textured vegetable protein.
Some Chinese recipes contain soy sprouts and soya sauce and should be avoided. Soya can be found in many readymade meals like pot noodles, tinned spaghetti.
It is present in crisps like Quavers and Monster Munch and in most bread bought in the supermarkets.
After a reaction to soya, your child should be provided with advice about what to do if they have another reaction. The plan is usually written down – Allergy Management Plan.
Mild reaction – hives, swelling or vomiting, but no breathing problems or faintness:
If possible, get the child to spit out the food. Give an antihistamine.
Severe reaction – difficulty breathing(wheezing, noisy breathing, blue colour); swelling in the throat(noisy breathing, drooling); feeling faint or dizzy, looking very pale(lie the child down with their legs raised).
Get help straight away and dial 999 stating “anaphylaxis” (ana-fil-ak-sis).If you have an adrenaline pen – use it.
It is important to inform the nursery/school and any after school clubs. Any other carers will also need to know.
Half of children with soya allergy will outgrow it by seven years of age. Nearly 70% of children outgrow by ten years of age. If there has not been a reaction for a long time an oral challenge may be suggested.
There is no cure for soya allergy at present.