In many cases, soy allergy starts with a reaction to a soy-based infant formula. Although most children eventually outgrow a soy allergy, it can persist into adulthood. Often, signs and symptoms of soy allergy – such as hives or itching in the mouth – are mild. In rare cases, soy allergy can cause a life-threatening allergic reaction (anaphylaxis).

If you or your child has a reaction to soy, let their doctor know. Tests can help confirm a soy allergy. If you have a soy allergy, you’ll need to avoid products that contain soy. This can be difficult, however, as soy is found in many foods, such as meat products, bakery goods, chocolate and breakfast cereals.

Signs and Symptoms of Soy Allergy

Soy allergy symptoms can include:

Abdominal pain, diarrhea, nausea or vomiting
Bloody stool (this is a common symptom from soy-based formula)
Hives, itching or itchy, scaly skin (eczema)
Redness of the skin (flushing)
Swelling of the lips, face, tongue and throat or other parts of the body
Tingling in the mouth
Wheezing, runny nose or trouble breathing
As mentioned above, soy allergy in infants often begins with the introduction of a soy-based formula. Soy allergy can develop when a child is switched to a soy-based formula after an allergic reaction to a milk-based formula.