The common characteristic of all canned gluten-free soups is that they do not contain more than 20 parts per million of wheat, barley, rye or other forms of wheat gluten. These soups are intended to be safe for people with gluten allergies or celiac disease to consume.
Gluten is used as a thickener in many canned soups, and some soups contain gluten-based ingredients such as pasta or barley. Gluten-free soups use alternate grains, gluten-free pastas and alternative thickeners to minimize their gluten content.
Although soups with less than 20 parts per million of gluten can legally be labeled "gluten-free" in the United States, this amount of gluten is sufficient to cause a reaction in extremely sensitive individuals. 20 parts per million is the standard threshold for gluten-free labeling because most people with gluten allergies or sensitivities can tolerate this amount of gluten without symptoms.
Amy's Kitchen, Bookbinders Specialties, Campbell's Soup, College Inn, Frontier Soup, Progresso, Swanson and Wolfgang Puck all market gluten-free soups. Healthy Choice is one major brand that does not certify any of its products as gluten-free, including those that do not appear to have gluten on the ingredients list. Frontier Soup certifies its gluten-free soups to a more rigorous standard of 5 parts per million of gluten, making it less likely to cause a reaction in individuals who are very sensitive to gluten.