onion
Vegetables
Is onion high in gluten?
Is onion high or low in gluten? See its exact rating, how much counts as a portion, and its FODMAP, salicylate, oxalate and diet compatibility in one place.
Related checkers
Compare onion across criteria
Sensitivity notes
Why gluten food checker matters
Gluten is a protein found in wheat, barley, rye, and their derivatives. People with celiac disease, gluten sensitivity, or wheat allergy need to avoid gluten to prevent digestive and systemic symptoms.
- Learn to read labels carefully - gluten hides in many products
- Be aware of cross-contamination in shared kitchens and restaurants
- Look for certified gluten-free products for safety
- Oats are naturally gluten-free but often cross-contaminated
- Give your gut time to heal - improvement may take months
Sensitivities
What onion contains
FODMAPs
Histamine & Amines
Plant compounds
Irritants
Additives
Allergens
Diet fit
Where onion fits
Therapeutic diets
Lifestyle diets
Religious diets
What to know about onion
Onion is graded E for fructans and E for total FODMAPs, the top of our scale, which is why it is the single most common trigger people uncover once they start logging food against symptoms. The reaction is a carbohydrate problem rather than an allergy: onion is A for histamine, A for oxalates, A for lectins and A for nightshades, so if onion bloats you the fructans are almost certainly the mechanism. It also grades E for low fermentation SIBO plans. The frustrating part is that fructans are water soluble and heat stable, so caramelizing, slow simmering or fishing the pieces out of a sauce does not make onion any safer, and onion hidden in stock, gravy and spice blends is why so many people react to restaurant food they cannot account for.
Watch for
- Fructans and total FODMAPs both graded E, the highest tier we use, and the grade does not soften between raw and cooked onion
- Cooking is not a fix: fructans dissolve out of the onion into the pan and stay in the liquid, so straining the pieces out leaves the trigger in the sauce
- Hidden onion drives most unexplained flare-ups: stock cubes, gravies, curry pastes, spice rubs, chips and anything listed as seasoning or natural flavor
- Graded E for low fermentation SIBO, so onion is usually one of the first things pulled when working through a SIBO protocol
- Clean on the rest of the chemistry (histamine A, oxalate A, lectin A, nightshade A, with only a borderline B for histamine liberation), which is why an onion reaction is nearly always intolerance rather than allergy
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Gluten Guide
Everything you need to know about gluten sensitivity and smart food choices.
Gluten is a protein found in wheat, barley, rye, and their derivatives. People with celiac disease, gluten sensitivity, or wheat allergy need to avoid gluten to prevent digestive and systemic symptoms.
Sensitivity varies widely. What triggers one person may be fine for another. Track your reactions to find your personal threshold.
These foods are generally well-tolerated for Gluten sensitivity:
View all safe options
These foods have moderate levels and may be tolerated in small amounts:
These foods are high in gluten and may trigger symptoms:
View full list
If you're sensitive to Gluten, consider these strategies:
- 1Learn to read labels carefully - gluten hides in many products
- 2Be aware of cross-contamination in shared kitchens and restaurants
- 3Look for certified gluten-free products for safety
- 4Oats are naturally gluten-free but often cross-contaminated
- 5Give your gut time to heal - improvement may take months
Pro tip: Keep a food diary to track your reactions. The Triggerbites app makes this easy with automatic pattern detection.
Want personalized tracking?
Download Triggerbites to log meals, track symptoms, and discover your unique triggers.
Get the AppFAQ
Is onion high in Gluten?
Gluten: low signal for most people.
Can I still eat onion if I'm sensitive to Gluten?
Usually fine in normal portions.
What else should I check?
Check FODMAPs, Fructans, and Low Fermentation next for a fuller picture.