Onions and garlic for cats: toxic even when cooked

The short answer

Onions, garlic, leeks, chives and shallots all belong to the allium family, and all of them are toxic to cats. The PDSA says onions are the most toxic, but garlic, chives and leeks are “also toxic, even when cooked or dried”. They damage red blood cells and can cause anaemia, with signs that may only show one to five days later. If your cat has eaten any, contact your vet or an out-of-hours vet now, even if your cat seems well.

Which foods are the problem

The PDSA names onions (including spring onions and shallots), garlic, chives and leeks. Cats Protection describes onion, garlic “and other members of the allium family of vegetables, whether fresh, cooked or dried” as potentially “extremely toxic”. The ASPCA lists onion, garlic, leek and chives among plants toxic to cats, so a garden or window-box plant counts as well as food.

Cooking does not make them safe. The PDSA answers “Can cats eat cooked onions?” with a plain no: cooked onions, shallots, garlic, chives and leeks “are all toxic to cats”.

Hidden in other food

Alliums are often an ingredient rather than a vegetable on the plate. The PDSA warns that onion and garlic “can be found in many pre-made foods like sauces and baby food”, and says to keep dirty plates and jars out of a cat’s reach. Cats Protection advises not feeding table scraps and asking guests not to either.

The sources above do not mention onion or garlic powder by name; they say “dried”. If your cat ate food seasoned with onion or garlic in any form, tell your vet.

Why alliums harm cats

The PDSA says alliums are thought to contain disulphides and thiosulfinates, compounds that damage red blood cells and so cause anaemia. The ASPCA describes the same effect, “gastrointestinal irritation and red blood cell damage”, and adds that cats are more susceptible than dogs. Dogs are at risk too: the ASPCA says dogs “are also at risk depending on the amount ingested”.

Signs to watch for, and when

Signs come in two waves, according to the PDSA:

Cats Protection lists vomiting, abdominal discomfort and lethargy. Because the signs of anaemia can take up to five days to appear, a cat that looks normal soon after eating alliums still needs a call to the vet.

What to do now

1. Take away any remaining food and anything else your cat could reach.
2. Contact your vet or an out-of-hours vet now, even if your cat seems well. The PDSA says to contact your vet “straight away” if you see your cat eating onions, garlic or leeks.
3. Tell the vet what was eaten, roughly how much and when. The RSPCA says the vet will want the exact name of the substance, roughly how much and how long ago. Cats Protection suggests taking a sample with you if possible.
4. Follow the vet’s advice. Cats Protection says the vet may ask you to bring your cat in or may advise over the phone.

What not to do: the PDSA says “Don’t attempt to make your cat vomit yourself at home”, and the RSPCA says never try to treat or medicate a cat yourself. Do not wait for symptoms either.

The outlook is good with prompt care. The PDSA says that “with treatment, most cats recover completely” and that lasting problems or death are very rare.

Garlic is not a flea treatment

The PDSA answers the question “Does garlic treat fleas?” directly: there is no evidence that garlic treats fleas, and it “should never be given to cats, even in small doses”.

Other dangers for cats and dogs

For plants, read lilies and cats: every part of a lily, including pollen and vase water, is poisonous to cats. If you share your home with a dog, see grapes and raisins for dogs, chocolate poisoning in dogs and xylitol and dogs. Travelling with your cat? See pet travel from the UK to the EU.

Before you act

This page reports what veterinary charities publish; it is not veterinary advice. The PDSA page on onion and garlic poisoning in cats has the full detail. If your cat has eaten something with onion or garlic in it, call the vet before you read further.