Soy is a member of the legume family, which also includes peas, lentil, beans, and peanuts. Soy is a common food allergy in infants and young children, but is rare in adults. Most children will outgrow their soy allergy by 4-6 years of age. There is little cross-reactivity between soy and other legumes: the chance of a reaction to another legume is only about 5%.
Avoiding soy can be difficult as it is found in may processed foods. Reading labels very important. If the label is unclear, contact the manufacturer.
Avoid foods which contain
These foods may contain soy:
Most soy allergic individuals can safely eat soy lecithin and soy oil
If you are allergic to cow milk and soybean and need an alternative for baking, you may want to try Vance's DariFree milk alternative. It's made from potatoes (it is milk, soy, rice, gluten free), and patients tell me that it works very well as a milk substitute for cooking.