Onion and garlic poisoning in dogs


  • Onions, garlic, and leeks are from a group of plants called alliums, which are all toxic to dogs and cats.
  • Symptoms of onion and garlic poisoning include vomiting, diarrhoea and a reduced appetite.
  • Alliums contain toxins called disulphides and thiosulfinates which can damage red blood cells, causing anaemia.
  • If your dog has eaten onions, garlic or leeks, you should contact your vet as soon as possible.
  • Dogs usually recover well with treatment.

Can dogs eat onions?

  • Dogs shouldn’t eat onions because they are part of a group of plants called alliums, which are all toxic to dogs.
  • Garlic, chives and leeks are all also alliums. All parts of these plants are toxic to dogs, even when cooked or dried.
  • Alliums are thought to contain toxins called disulphides and thiosulfinates that cause damage to red blood cells.
  • Some dogs are more sensitive to onion and garlic poisoning than others.
  • Remember that onions and garlic can be found in many pre-made foods, such as sauces and baby food.


Symptoms can start within 24 hours after eating onion, garlic or leeks but more commonly take a few days to appear. Symptoms may include:

Onion and garlic poisoning can also lead to anaemia (low red blood cell count). Symptoms of anaemia include trouble breathing and lethargy (low energy). These symptoms may occur 1-5 days after eating the onion, garlic or leek.

Very rarely, onion and garlic poisoning can cause seizures.


  • Diagnosis is based on the symptoms or whether you have seen your dog eating onions, leeks or garlic.
  • Urine and blood tests might also be carried out.


  • If it’s within four hours of eating onion, garlic or leeks, your vet will probably give your dog an injection to make them vomit. It is important not to attempt this yourself at home.
  • Your vet may also give your dog activated charcoal to help absorb any remaining toxins in the stomach.
  • Your dog may also be put on a drip to keep them hydrated and kept in the hospital for observation.
  • Treatment for any symptoms might also be given, for example, medications to stop vomiting or seizures.
  • Your dog might also need to have blood tests to check whether they are anaemic.


With treatment, most dogs recover well. It’s very rare for onion, garlic or leek poisoning to cause ongoing severe problems or death.

When to contact your vet

It is best to treat poisoning as soon as possible, so contact your vet if you see your dog eating onions, garlic or leeks or if you are concerned your dog is showing symptoms. You can also call the Animal Poisoning Line for advice.



Can dogs eat cooked onions?

Cooked onions, garlic and leeks are still toxic to dogs and should be kept out of their reach. Remember that sauces, baby food and other pre-made foods may contain onions or garlic.

Does garlic treat fleas?

No, there is no evidence that garlic can be used to treat fleas and it should never be given to dogs, even in small doses. Always use veterinary-approved flea treatments

Can dogs eat potatoes?

Potatoes are not in the allium family of plants. However, raw potatoes can be toxic to dogs. If you are feeding potatoes to your dog, they must be cooked and plain.

Published: September 2022

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Written by vets and vet nurses. This advice is for UK pets only. Illustrations by Samantha Elmhurst.