A soy allergy, like any allergy, is when your immune system identifies soy proteins as harmful. When you come into contact with these proteins, your immune system releases histamines, which then cause your allergic symptoms.

As a high-protein member of the legume family, soy is a common ingredient in infant formulas and is an important source of protein worldwide. Many vegetarians and vegans rely on soybeans as a great way to get protein in their diets.