Hidden sources of gluten: where it hides and how to check

The most common hidden sources of gluten are barley malt (malt extract, malt flavoring, malt vinegar), traditional soy sauce, flour-thickened sauces and gravies, stock cubes and seasoning blends, licorice candy and beer. Gluten can also come from additives such as colorings, flavorings, starches and thickeners made from gluten grains (NIDDK).

Gluten is a protein found in wheat, barley, rye and triticale. Bread and pasta are obvious. The harder part is the long tail of foods where a gluten grain is a minor ingredient, a processing aid or a cross-contact risk. If you are newly diagnosed, our celiac disease and gluten-free eating guide covers the basics first.

In the US, wheat is one of the nine major food allergens, so packaged foods regulated by the FDA must name it, either in the ingredient list or in a "Contains" statement (FDA). Barley and rye are not on that list. A product can contain barley malt without a "Contains" line that mentions it, so always read the full ingredient list.

In the UK and EU, "cereals containing gluten" are one of the 14 allergens that must be emphasized in the ingredient list, usually in bold, and this covers wheat, rye, barley and oats (Coeliac UK).

Two more reasons to read the label every time: recipes change without warning, and a product that was fine last month may be made differently now. Our guide to reading food labels for allergens goes deeper.

Malt is usually made from barley. The Celiac Disease Foundation lists malted barley flour, malted milk, malt extract, malt syrup, malt flavoring and malt vinegar as gluten sources, along with brewer’s yeast.

• Breakfast cereals: corn flakes and rice puffs often contain malt, even though corn and rice are naturally gluten-free.
• Malted drinks: malted milk and malted milkshakes.
• Malt vinegar: found in chips seasonings, pickles, dressings and condiments. The FDA does not allow malt extract, malt syrup or malt vinegar made from barley in foods labeled gluten-free.
• Brown rice syrup: may be made with barley enzymes, so it is worth checking.

Other vinegars, such as balsamic, cider, wine and spirit (distilled) vinegar, are listed as gluten-free by Coeliac UK.

Traditional soy sauce is brewed with wheat. The Celiac Disease Foundation notes that tamari made without wheat is gluten-free, but not every tamari is made that way, and Coeliac UK lists tamari as a "need to check" item. Look for a gluten-free label on the bottle.

Soy sauce also turns up inside other things, which is where it gets easy to miss:

• Teriyaki and other glazes, stir-fry sauces and marinades.
• Marinated tofu and pre-seasoned meats.
• Salad dressings, which can also contain malt vinegar or flour.
• Sauces and gravies thickened with wheat flour, and cream sauces made with a roux.

The Celiac Disease Foundation also flags cream-based soups (often thickened with flour), soups containing barley, and cheesecake fillings that use wheat flour.

Coeliac UK’s gluten-free checklist puts stock cubes, gravy granules, blended and powdered seasonings, curry powder, packet and jarred sauces and mixes, and canned or packet soups in its "need to check" column. Single herbs and spices, salt, ground pepper and mustard powder are listed as gluten-free.

The "why" column draws on the NIDDK’s note that colorings, flavorings, starches and thickeners can be made from gluten grains, and on the Celiac Disease Foundation’s list of foods that may contain gluten. It points out that starch or dextrin on meat and poultry could come from any grain, including wheat.

Many people are surprised to learn that licorice candy usually contains wheat flour. Coeliac UK lists liquorice sweets as not gluten-free, while plain liquorice root is gluten-free. Gluten-free licorice exists, so look for the label. Candy and candy bars in general are on the Celiac Disease Foundation’s "may contain" list.

Beer, ale, lager and malt beverages are made from gluten grains and may contain gluten (NIDDK). Some points that trip people up:

• Beer labeled gluten-free is a different product from regular beer. Coeliac UK lists gluten-free beers and lagers as gluten-free, and regular ales, beers, lagers and stouts as not gluten-free.
• "Crafted to remove gluten" beer is made from barley and then treated. In the US it cannot be labeled gluten-free, according to Gluten Free Watchdog’s summary of the TTB ruling.
• Flavored liquors may contain gluten, so check with the maker (NIDDK).
• Coeliac UK also lists cider, wine, spirits, port and sherry as gluten-free.

Some of the easiest gluten to miss is in foods that start out gluten-free. The Celiac Disease Foundation lists several in its "may contain gluten" group:

• French fries: potatoes are gluten-free, but fries can be coated in a wheat flour batter or cooked in oil shared with breaded foods.
• Tortilla chips and tortillas: multigrain or "artisan" versions that aren’t fully corn-based.
• Rice puffs and corn flakes: often made with malt.
• Granola and energy bars: usually made with regular oats, which are often contaminated.
• Meat substitutes: veggie burgers, sausages, imitation bacon and imitation seafood made with seitan, which is wheat gluten.
• Restaurant eggs: plain eggs are gluten-free, but some restaurants add pancake batter to their eggs.
• Soba noodles: buckwheat noodles, but some are made with only part buckwheat flour plus wheat.

The pattern is the same each time: a gluten-free base, plus a wheat or barley ingredient, a shared fryer or contaminated oats. When a food is usually gluten-free, it is worth asking what has been added to it.

The FDA says the majority of oral medicines contain no gluten or virtually none. Wheat-derived ingredients are rare, and where present the FDA estimates they would add no more than 0.5 mg of gluten per dose. Gluten labeling on medicines is not required, though.

1. Check the inactive ingredients. On over-the-counter medicines they are on the Drug Facts label. For prescriptions, they are usually in the "Description" section of the prescribing information.
2. Ask your pharmacist to check any medicine you take regularly, and tell them you have celiac disease so it is on your record.
3. Ask the same question about vitamins and herbal or nutritional supplements, which the Celiac Disease Foundation lists as products to verify.
4. If a medicine changes brand or manufacturer, check again.

The Celiac Disease Foundation also lists a few non-food items to check: communion wafers, lip products (because they can be swallowed) and wheat-based play dough, which children may handle and then touch their mouths.

On cosmetics more broadly, Celiac Canada notes that gluten absorbed through the skin has not been shown to harm people with celiac disease. The concern is swallowing small amounts, which is why lipstick, lip balm and toothpaste get the most attention. Studies it describes found most such products contained little or no gluten. Washing your hands ahead of meals covers the rest.

1. Start from plain, single-ingredient foods where you can: plain meat, fish, eggs, rice, potatoes, fruit and vegetables.
2. For anything packaged, read the full ingredient list, not just the "Contains" line. Look for wheat, barley, rye, malt, brewer’s yeast and triticale.
3. Prefer products labeled gluten-free for higher-risk foods like oats, flours, sauces and seasonings. See gluten-free vs celiac-safe for what that label does and doesn’t promise.
4. When unsure, contact the manufacturer or skip it for now.
5. Eating out? Sauces, marinades and shared fryers are the big ones. Our eating out with celiac disease guide has the questions to ask.

Hidden gluten can make food feel like a minefield at first. With time, most people build a short list of trusted products and a quick label habit, and checking becomes routine. A dietitian who knows celiac disease can speed that up.