Going gluten-free means cutting out wheat, barley, and rye, but the real challenge is everything else that contains gluten without being obvious about it. Soy sauce, potato chip seasoning, certain medications, and even some lip balms can contain enough gluten to cause problems. Knowing the obvious sources is the easy part. This guide covers the hidden ones.
Hidden Gluten in Processed Foods
Many processed foods contain gluten-derived ingredients that don’t mention wheat, barley, or rye by name. If a product isn’t labeled “gluten-free,” watch the ingredients list for: modified food starch, hydrolyzed vegetable protein, hydrolyzed plant protein, textured vegetable protein, dextrin, maltodextrin, glucose syrup, caramel color, malt flavoring, malt extract, malt vinegar, and brown rice syrup. Any of these can be sourced from gluten-containing grains.
Some specific foods catch people off guard. Soy sauce is made with wheat (tamari is the gluten-free alternative). Miso soup base may contain barley. Potato chips seem safe, but the seasoning often includes malt vinegar or wheat starch. Distilled white vinegar is fine, but malt vinegar is not.
Grains That Need Extra Caution
Oats are naturally gluten-free, but they’re one of the most frequently cross-contaminated grains on the market. Oats are commonly grown near, transported with, or processed alongside wheat, barley, and rye. The FDA doesn’t classify oats as a gluten-containing grain, but the agency acknowledges that oat products can carry “potentially significant levels” of gluten from cross-contact. If you eat oats, look for products specifically certified gluten-free, which must test below 20 parts per million (ppm).
On the flip side, some grains that sound like they might contain gluten are perfectly safe. Buckwheat, despite the name, is a gluten-free pseudocereal unrelated to wheat. Quinoa and amaranth are also naturally gluten-free. Rice, corn, millet, sorghum, and teff are all safe choices. Just make sure any packaged version hasn’t picked up cross-contact during processing.
Beer, Spirits, and Other Drinks
Beer, ale, lager, and malt beverages are all made from gluten-containing grains and are off-limits. Some breweries market beers as “crafted to remove gluten” or “processed to remove gluten,” but federal labeling rules require those products to carry a warning: the gluten content cannot be verified, and the product may still contain gluten. These are not the same as gluten-free beers brewed from sorghum, rice, or other safe grains.
Distilled spirits are a different story. Even when distilled from wheat, barley, or rye, the distillation process removes gluten proteins. Vodka, gin, whiskey, and bourbon are generally considered safe, provided no gluten-containing ingredients were added after distillation. Wine and hard cider made from grapes or apples are naturally gluten-free. If you want the simplest rule: stick to products actually labeled “gluten-free,” which can only appear on alcohol made without gluten-containing grains or verified through good manufacturing practices.
Medications and Supplements
This one surprises a lot of people. The inactive ingredients in pills, known as excipients, sometimes include wheat-derived starches. These fillers give tablets their bulk and help them break apart in your stomach. Most pharmaceutical starches come from corn, potato, or tapioca, but wheat starch shows up too.
Ingredients to flag on medication labels include pregelatinized starch, sodium starch glycolate, dextrates, dextrins, and maltodextrin. All of these can come from any starch source, including wheat. The label often won’t specify the source, so the only reliable way to confirm is calling the manufacturer directly. This applies to both prescription drugs and over-the-counter supplements. Your pharmacist can help identify gluten-free alternatives if needed.
Lip Products and Oral Care
Gluten in a hand lotion won’t cause a reaction since gluten must be ingested to trigger symptoms. But products that go on or near your mouth are a different concern. A study testing 66 oral care and cosmetic products (toothpastes, mouthwashes, lip balms, and lipsticks) found that 6% contained gluten above 20 ppm, even though none listed wheat, barley, or rye in their ingredients. Three toothpastes and one lipstick exceeded the threshold. The amounts are small, but for someone with celiac disease, routine daily exposure from a toothpaste used twice a day adds up.
Cross-Contamination at Home
If you share a kitchen with people who eat gluten, cross-contamination is a real concern, though the risks aren’t always where you’d expect. Research testing shared kitchen equipment has produced some nuanced findings. Toasting gluten-free bread in a toaster previously used for regular bread, and using a wooden spoon that stirred gluten-containing pasta, both tested below 20 ppm in controlled experiments.
The higher-risk situations involve shared cooking liquids. Boiling gluten-free pasta in water that was used for regular pasta, and frying gluten-free food in oil that previously fried breaded items, both produced contamination above safe thresholds. Airborne flour is another concern. Wheat flour can stay suspended in the air and settle on surfaces and uncovered gluten-free ingredients. If someone is baking with wheat flour, keep gluten-free foods sealed and away from the area.
Eating Safely at Restaurants
Restaurants present the most unpredictable risk. Calling ahead is worth the effort. Ask whether they have a gluten-free menu, whether staff have completed any gluten-free training, and how they handle gluten-free orders to prevent cross-contact.
When ordering, get specific. Ask how the dish is prepared and whether the kitchen uses separate prep space, separate cookware, and a dedicated fryer for gluten-free items. Shared fryers are a known contamination source. Ask about less obvious ingredients too: spice blends, thickeners, coatings, and garnishes can all contain hidden gluten. Croutons removed from a salad still leave gluten behind. A sauce thickened with flour won’t be listed on most menus.
If your food arrives looking different than expected, or appears breaded, or seems off in any way, ask before eating. Be direct: “This looks breaded. Are you sure it’s gluten-free?” It’s better to slow down a meal than to spend the next few days dealing with symptoms.
Understanding “Gluten-Free” Labels
In the United States, a product labeled “gluten-free,” “no gluten,” “free of gluten,” or “without gluten” must contain less than 20 ppm of gluten. That’s 20 milligrams per kilogram of food, and it’s the lowest level that can be reliably detected with current testing methods. This threshold applies to packaged foods regulated by the FDA.
The international standard, set by the Codex Alimentarius (the food standards body run by the WHO and FAO), also uses 20 ppm as its benchmark. So if you’re traveling internationally, the threshold is generally consistent, though enforcement and labeling practices vary by country. When in doubt abroad, stick to whole, unprocessed foods you can verify yourself: plain grilled meats, fruits, vegetables, rice, and potatoes.