Soya is one of the 14 allergens that need to be clearly highlighted on the packaging of any food that contains it. An allergy to soya may not be as common as allergies to milk, eggs, peanuts or fish, but is just as life threatening.
Soya is a legume (a bean), which is often eaten cooked. It is also added to many other foods after being processed in some way. They're often dried and then made into soya flour and added to many different types of food dishes - even ones which you wouldn't expect to contain soya (baked beans, for instance!). Soya is also made into Textured Vegetable Protein (TVP), soya meat, soya chunks and soya milk. Soya milk is often used as an alternative to cow's milk and breast milk. When the immature bean in the pod is used, the product is called 'edamame', which is a common ingredient in Asian cooking, so those with an allergy to soya will also need to steer clear of edamame.
Allergic reactions to soya among children are often mild, and may just cause a rash. But they are not always mild and the allergic reaction can affect the whole body, leading to anaphylactic shock, which is always a life threatening medical emergency.
For some people, their symptoms can involve their digestive system instead, giving rise to symptoms such as stomach pains, diarrhoea, vomiting, acid reflux and colic. Very rarely, Food Protein Induced Enterocolitis Syndrome (FPIES) occurs, leading to diarrheoa and severe and repeated vomiting - this can happens 2-3 hours after the exposure to the soya allergen (as with other allergens). This is more common in babies and very young children, who are much more susceptible to dehydration and other complications, increasing the amount of impact on them.