Soy allergy is so common that it is in the Top 8 list of foods that provoke an allergic reaction. According to Eliot Herman, Ph.D., a researcher with the U.S. Department of Agriculture approximately 5 to 8 percent of children and 1 to 2 percent of adults are allergic to soy. According to the Food and Drug Administration, an estimated 0.2 percent of Americans are allergic to soy.  The Food Allergen Labeling and Consumer Protection Act of 2004 lists soy as one of the eight most common food allergies.