Is Onion Toxic to Cats and Dogs?
Onions are severely toxic to both cats and dogs — they destroy red blood cells and cause anemia. Cats are especially sensitive. Call a vet.
Potentially life-threatening — treat any exposure as an emergency.
Potentially life-threatening — treat any exposure as an emergency.
In an emergency, do not wait.
Medical disclaimer: This tool is for general information only and isnot a substitute for veterinary diagnosis or treatment. Toxicity depends on the amount, your pet’s size, and health history. If your pet may have ingested something harmful, contact your veterinarian or a poison control hotline ((888) 426-4435 / (855) 764-7661) immediately — do not wait for symptoms to appear.
What is Onion?
Onions are severely toxic to both cats and dogs — they destroy red blood cells and cause anemia. Cats are especially sensitive. Call a vet.
Also known as: onions, allium, scallion, green onion, shallot.
Symptoms to Watch For
🐕 In Dogs
- Destruction of red blood cells (hemolytic anemia)
- Lethargy, weakness, and pale gums
- Reduced appetite and vomiting
- Dark or red-tinged urine
🐈 In Cats
- Red blood cell destruction (cats are especially sensitive)
- Weakness and pale gums
- Reduced appetite, vomiting, drooling
- Dark or red-tinged urine
What to Do If Ingested
- Remove any remaining onion from reach.
- Note the amount and form (raw, cooked, powder are all toxic).
- Call a veterinarian or poison hotline, especially for a large amount.
Steps apply to both cats and dogs. When in doubt, call a vet or poison hotline before acting.
When to Call the Vet Immediately
Call your veterinarian or a poison control hotline right away if you notice any of these:
- A large amount or onion powder was eaten
- Weakness, pale gums, or lethargy
- Dark or red urine
- Rapid breathing or collapse
Frequently Asked Questions
Frequently Asked Questions
Are cooked onions safer than raw?
No. Cooking does not destroy the toxic compounds (N-propyl disulfide and related thiosulfates). Raw, cooked, dehydrated, and powdered onions are all toxic, and onion powder is especially concentrated.
How much onion is dangerous?
Cats are far more sensitive than dogs, and toxicity can build up over several small meals, not just one big one. Even a small amount can affect a cat, while dogs usually need a larger dose. Call a vet with the amount and your pet's weight.
What are the signs of onion poisoning?
Onions destroy red blood cells, causing anemia. Watch for weakness, lethargy, pale gums, reduced appetite, and dark or red-tinged urine. Symptoms may appear a few days after ingestion.
Sources
This entry is reviewed against the following authoritative veterinary sources.
Last reviewed: 2026-07-11