Susan,
You may be eating soy flour and don't know it.
http://www.allergyny.com/IndividualAllergies.htm

Here's the quote from the link above on pet and food allergies, including
soy:

"Soybean flour is often added to cereal flour and is used extensively in the
baking industry. The majority of breads contain some soy flour. Pastries,
cakes, biscuits, and baby foods may contain soy flour. It is also used in
the manufacture of sausages, processed meats, hamburgers, and other meat
products (Table VI) . Fermented soybean may be used in the preparation of
soy sauce or Worcestershire sauce. Fermented soy is in wide use as a food in
the Far East.
Soy is so widely distributed in processed foods that avoidance of soy in the
diet is very difficult. Soy may find its way into a food product when added
as a compound ingredient. For example, if margarine is added to a food
product it will be listed as such, but soy present in the margarine itself
will not be listed on the ingredients panel.

Soy protein isolate or concentrate may be used to emulsify fat in food
products and may thus be used in the manufacture of ice cream, mayonnaise,
and a variety of other liquid fat- or oil-containing foods. The concentrate
or isolate may also be used in soymilk and as a protein concentrate added to
health foods and high-protein biscuits. Other foods that may contain soy
include pureed and cereal baby foods, margarine, and white and brown bread
(Table VI)."