As someone with celiac disease, you need to avoid eating anything that contains wheat, barley or rye. Barley grass, then, would seem to be strictly off-limits. However, the analysis is more complicated than that; barley grain contains gluten, but barley grass, if harvested early enough, should not. The U.S. Food and Drug Administration considers barley grass to be safe on a gluten-free diet, providing it doesn't contain any fragments of the grain. However, you should talk with your doctor about whether the benefits of consuming barley grass as part of a gluten-free diet outweigh the risks.
People with celiac disease suffer intestinal damage due to the protein gluten. As of 2011, no drug treatment exists for celiac disease; the only choice is to avoid all foods that contain gluten. Those with celiac disease need to steer clear of most bread and grain products, along with a multitude of processed foods, such as canned soups, sauces and salad dressings. Most "foods to avoid" lists available from major medical centers for celiac patients include barley grass.
However, pure barley grass shouldn't contain gluten. As the barley plant grows, it first produces leaves -- the grass -- and finally culminates in the seeds. Those seeds -- the grain portion of the plant -- contain all the plant's gluten protein. When farmers grow barley grass, they can take care to harvest it before the plants begin going to seed, meaning the final grass product would be gluten-free.
Expert celiac disease dietitian Tricia Thompson acknowledges that barley grass can be gluten-free. However, a particular crop of barley grass may possibly contain some of the seeds, or grain, from early-sprouting plants. Therefore, she advises anyone with celiac disease who's considering purchasing or consuming a product that contains barley grass to determine if the product has been tested for gluten. Because barley gluten doesn't always register well on tests for gluten cross-contamination, Thompson also advises asking about the results from a specific, more accurate gluten test, the R5 ELISA test.
In practice, it may be simpler for celiacs to avoid all products with barley grass, even if they claim to be gluten-free. That's the approach recommended by Gluten Intolerance Group President Cynthia Kupper. Kupper notes that the nutritional content in barley grass doesn't beat the nutrients you can obtain from a wide variety of fruits and vegetables. She also recommends substituting alfalfa grass for barley grass, since alfalfa plants contain no gluten even once they've gone to seed.