a note about shredded cheeses-
There's another fairly persistent myth that shredded cheese may include a gluten ingredient as an anti-clumping agent. Anti-clumping agents used by cheese manufacturers include powdered cellulose, calcium carbonate and potato starch. Of these, only powdered cellulose can be made from a gluten grain (wheat, usually), but in that case, the manufacturer should call out the wheat on the product's label.
In the U.S & Canada., both Kraft and Sargento — two popular manufacturers of shredded cheese — consider their shredded cheeses to be gluten-free to the generally accepted 20 parts per million standard. Sargento adds that the powdered cellulose it uses in its shredded cheese is not derived from any gluten grain.