Dog Care
Can Dogs Eat Onions? Why They're Toxic and What to Do
No, dogs should never eat onions. Onions are toxic to dogs whether they are raw, cooked, fried, dried or powdered. They contain compounds that damage red blood cells and can cause a serious anaemia. Garlic, leeks, shallots, spring onions and chives belong to the same plant family and are harmful too. If your dog ate onion, call your vet.
Why are onions toxic to dogs?
Onions contain sulphur compounds, including N-propyl disulphide, that damage the red blood cells that carry oxygen around the body. The damaged cells break down, which can lead to haemolytic anaemia. The American Kennel Club notes that around 100 grams of onion per 20 kilograms of a dog's body weight can cause toxic effects, and the ASPCA lists onions, garlic and chives among foods to avoid.
Cooking does not make onions safe. Onion powder is concentrated, so small amounts can matter. Effects can also build up if a dog eats small amounts over several days.
How much onion is dangerous?
Using the AKC figure of about 100 g per 20 kg (roughly 0.5% of body weight), here is a rough picture. Smaller amounts can still cause problems, and onion powder is far stronger than fresh onion, so call your vet rather than relying on a number.
| Dog's weight | Fresh onion that may cause toxic effects |
|---|---|
| 5 kg (11 lb) | About 25 g, roughly a quarter of a small onion |
| 10 kg (22 lb) | About 50 g, roughly half a small onion |
| 20 kg (44 lb) | About 100 g, roughly one small onion |
| 40 kg (88 lb) | About 200 g, roughly one large onion |
Symptoms of onion poisoning in dogs
Stomach upset can appear within a day. Signs of anaemia are often delayed by a few days.
- Vomiting, diarrhoea, drooling, belly pain, loss of appetite
- Weakness, tiredness, reluctance to walk
- Pale gums
- Fast breathing or a fast heart rate
- Red or brown urine
- Collapse in severe cases
My dog ate onion: what to do
- Work out how much and in what form: fresh, cooked, powder, or in a dish such as gravy, stuffing or soup.
- Weigh your dog or use their last known weight.
- Call your vet or an animal poison control line straight away, even if your dog seems fine. Early treatment works best.
- Don't make your dog vomit unless a vet tells you to.
- Watch for delayed signs for several days and go back to the vet if your dog seems weak or has pale gums.
Hidden sources of onion
- Gravy, stock cubes and soups
- Stuffing, meatloaf, burgers and sausages
- Pizza, pasta sauce and curries
- Baby food, which sometimes contains onion powder
- Seasoning mixes and rubs
- Onion rings and crisps
Check other foods quickly with our can my dog eat this? food checker.
Frequently asked questions
Are cooked onions safe for dogs?
No. Cooking doesn't remove the compounds that damage red blood cells. Raw, cooked, fried and powdered onion are all toxic to dogs.
My dog ate a small piece of onion. Will he be okay?
A tiny piece is unlikely to cause serious harm in a large dog, but the risk depends on your dog's size and how much was eaten. Call your vet for advice, and watch for weakness or pale gums over the next few days.
Can dogs eat garlic?
No. Garlic is in the same family as onion and can damage red blood cells too. Garlic powder is concentrated.
How long after eating onion will a dog get sick?
Stomach upset can start within a day. Signs of anaemia, such as weakness and pale gums, are often delayed for a few days.
Are onions toxic to cats?
Yes. Cats are even more sensitive to onion and garlic than dogs. Call your vet if your cat eats any.
Sources
Guidance follows the American Kennel Club and the ASPCA Animal Poison Control Center. This article is general information, not veterinary advice.
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