Soy or soya as it is known in some parts of the world originates from the soy bean, which is a type of legume. However, soy is used in a wide variety of processed foods, so the list of products to be avoided by those with soy allergy is dauntingly long. As soy allergies are common, in both the EU and the US, any product containing soy must state this on the label. This common allergy often manifests itself in early childhood, usually as a reaction to some kind of soy-based baby product such as babyfood or formula milk. Breast fed babies may be sensitive to soy in the mother’s diet. Often children will outgrow this allergy, but some continue with the allergy into adulthood. Those with a family history of soy or other allergies are at increased risk.
Common symptoms include:
- Babies becoming unsettled or fussy after a feed, or experiencing stomach upsets such as diarrhoea or green stools
- A tingling or itching sensation in the mouth
- Hives or a rash
- Stomach pain, nausea, vomiting and/or diarrhoea
- A frequent runny nose
- Wheezing or difficulty breathing
In most cases symptoms cause discomfort but are not particularly serious. However, in rare cases, a soy allergy can result in anaphylaxis, a severe, often sudden reaction where the body goes into shock. Signs include difficulty breathing, flushing, racing or weak pulse, dizziness and loss of consciousness. Those who have been diagnosed as being at risk of anaphylaxis will have been diagnosed equipment for self-administration of Epinephrine (known as Adrenaline in the UK and Australia). If anaphylaxis is suspected, epinephrine should be administered immediately and an ambulance should be called. The patient must be taken to an emergency care centre whether or not Epinephrine has been administered.
If you believe that you or your child may be suffering from a soy allergy, you should go to see your doctor who may refer you to an allergy specialist for further investigation.
Aside from asking you general questions about what you have been eating and your symptoms, they might also perform a skin-prick test and/or a blood test. A skin-prick test involves exposing a small area of your skin to the proteins found in soy and waiting to see if a reddish lump appears which would indicate an allergy. A blood test can measure how your immune system reacts to soy. In some cases, under close medical supervision, with emergency medication and equipment at hand, an oral food challenge may be done, where the patient is given small amounts of soy or soy products to observe the reaction.
Management of the condition
If you suffer from a soy allergy then the only way to manage the condition is to avoid foods containing soy. Unfortunately, many foods do contain soy. This list includes, but is not limited to, soya beans, edamame beans (which are immature soya beans), soy sauce, soy milk (including some infant formula milks), soy protein, soy fibre, miso, natto, tamari, tempeh, teriyaki sauce, tofu, some bouillon cubes and ready-made broths, many processed meats (including some chicken nuggets), energy bars and canned foods. Soya flour is quite often used in breads, cakes, and baby foods. Look out also for textured vegetable protein (TVP) and hydrolysed vegetable protein (HVP).
It is best to avoid fast food restaurants and Asian cuisine as even if they dishes not contain soy products, they may have been cooked in soy oil or in the same oil as soy products.
Soy based lecithin, often used to improve the texture of chocolates and spreads, usually does not have to be avoided as it contains very little soy protein. Take advice from a medical practitioner if in doubt.
While soy is a legume, a soy allergy does not necessarily indicate that other legumes such as peas, peanuts and lentils need to be avoided.