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What Is Gluten Cross-Contamination?

And Why Should You Worry About It?


Updated June 18, 2014

Cross-contamination is when gluten-free food comes into contact with food that does contain gluten. Unfortunately, there are many ways for cross-contamination to happen in homes and restaurants. Here are a few safety tips to help prevent gluten accidents:

  • Don’t prepare gluten-free foods on the same surface used to prepare foods with gluten unless the surface has been thoroughly cleaned. (In restaurants, ask the chef to wipe down the grill before preparing your order.)

  • Make sure utensils have been thoroughly cleaned after preparing gluten-containing foods. Even better, have separate sets of utensils for gluten-free food preparation.

  • Don’t use the same toaster for gluten-free bread and regular bread. If your home isn't entirely gluten-free and you can only have one toaster, try to make it a toaster oven and get extra trays from the manufacturer for gluten-free toasting.

  • Don’t use the same sifter for gluten-free and regular flours. Clearly label the gluten-free sifter to avoid mistakes.

  • Don’t deep-fry gluten-free foods in the same oil used to fry breaded items. This is a particular risk in restaurants. You'll need to ask whether breaded and unbreaded items are fried in the same oil.

  • Watch out for crumbs in spreadable condiments (such as jellies, butter, cream cheese and dips) being shared in a household. Either have a duplicate container for the celiac person, or make sure the non-celiacs always dip into the container with a clean knife. (In my house, we put a clean knife out with each condiment, and my husband and stepdaughter use the clean knife to put some of the condiment first onto their plates, and then they use their own knives for spreading it onto their bread.)

  • Avoid using gluten-containing flours in kitchens where gluten-free food is prepared. Wheat flour can stay airborne for many hours and contaminate surfaces, utensils, and uncovered gluten-free food. In general, foods prepared in any place that is not gluten-free are at risk for contamination (for example, when equipment is inadequately cleaned after producing gluten-containing foods).

Cross-contamination is also the major reason why most commercial oats are considered unsafe for celiacs. While oat and wheat proteins may have some similarities, the major problem is that these two grains are usually grown next to each other in the fields, processed in the same grain elevators, milled with the same equipment, and transported using the same containers. Inevitably under these circumstances, the grains co-mingle and the oats become contaminated with gluten. Gluten-free oats are slowly becoming available.


American Celiac Disease Alliance.

Thompson T. "Gluten contamination of commercial oat products in the United States." New England Journal of Medicine 351: 2021-2022, 2004.

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