onion
Onion is genuinely toxic to dogs and cats — all forms, including powder, with damage that arrives days late. What every owner should know, stated plainly.
Also appears on labels as: onion powder · dried onion · dehydrated onion
What it is
Onion in any form: raw, cooked, dehydrated, or powdered. Allium compounds (N-propyl disulfide and kin) oxidize red blood cell hemoglobin into Heinz bodies, and the damaged cells are culled — enough exposure means hemolytic anemia. Cooking does not neutralize it; powder is MORE concentrated than fresh; cats are markedly more sensitive than dogs, and some dog breeds (Japanese breeds like Akitas and Shibas) run sensitive too.
Why it's in pet food
It shouldn't be — and in honest pet food it isn't. Onion reaches pets through human food: baby food with onion powder, gravy, soup, table scraps, and broths. The dictionary carries the term so a scanned label listing it is never silently matched past.
How Bowlmark scores it
Scores are deterministic math over the printed label — the rules below apply to every product identically, and nothing estimates or fills in a blank.
The engine now says what this page always said: onion carries a critical flag — matched in any form, it takes −60 on the additives pillar and caps the Universal Score outright, so no label listing onion can score well. The gap this page once narrated was closed in the 2026-08 matcher update; the score and the warning finally agree. Treat any deliberate onion listing on a pet product as disqualifying — which is exactly what the cap does.
For dogs
Signs lag exposure by one to several days: lethargy, weakness, pale gums, red-to-brown urine, fast breathing. A meaningful single dose (roughly a small onion's worth for a mid-size dog, far less for small dogs) or repeated small doses both count. If your dog ate onion in quantity — or onion powder in any concentrated form — call your vet or an animal poison control line now, not at symptom time.
For cats
Cats are the most sensitive common companion species — small amounts of onion or onion powder (a spoonful of oniony baby food, licked gravy) can matter. Same delayed signs, same instruction: known exposure is a call-the-vet event before symptoms appear.
Common questions
Answers come from this entry and the scoring rules above — reviewed before publish, like everything else on this page. For anything about your own pet, your vet knows best.
Can dogs eat onion?
No. Onion is toxic to dogs in every form — raw, cooked, dehydrated, or powdered — and cooking does not neutralize it. Its Allium compounds damage red blood cells, and signs lag exposure by one to several days: lethargy, weakness, pale gums, red-to-brown urine, fast breathing. If your dog ate onion in quantity, or onion powder in any concentrated form, call your vet or an animal poison control line now.
How much onion is dangerous for a dog?
A meaningful single dose is roughly a small onion's worth for a mid-size dog — far less for small dogs — and repeated small doses count too, because the red-cell damage accumulates. Powder is more concentrated than fresh, so spice-level amounts go further than they look.
Is onion powder dangerous for cats?
Yes — cats are the most sensitive common companion species, and small amounts of onion or onion powder (a spoonful of oniony baby food, licked gravy) can matter. The signs arrive days late, so known exposure is a call-the-vet event before symptoms appear.
How does Bowlmark score onion?
Onion carries a critical flag: matched in any form, it takes 60 points off the additives pillar and caps the Universal Score outright, so no label listing onion can score well. That is the score agreeing with what this page says in words — treat any deliberate onion listing on a pet product as disqualifying.
Foods that list onion
No food on the shelf lists onion yet. Scan a bag that does and its label joins the catalog — versioned from the day it arrives.
Sources
Related ingredients
Further reading
Cite this page
Bowlmark. "Onion in pet food — what it is and how it scores." https://www.bowlmark.com/ingredient/onion
- Engine
- Methodology engine v1.1.0 · config 13c99e2f
- Verified
- Last verified August 21, 2026
No stored score to stamp yet — the engine and config above are the ones a scan runs today.