Why are Garlic and Onions Bad for Cats?

Caitlin Dempsey


A photo of a blue of garlic and an onion.

Cats are obligate carnivores, which means most of their diet comes meat. Still, a lot of cats enjoy nibbling on other types of food like grass, green beans, and even that cake that they can’t taste the sweetness of.

There are some types of foods, like chocolate, that should be strictly off-limits for cats. Plants in the Allium family are poisonous to cats. Members of this plant family include garlic, onions, leeks, shallots, and chives. Even small of amounts of these plants can be toxic to your feline companion.

Any form of these plants will be toxic, whether your garlic or onion is fresh, cooked, dried, or powdered. In fact, because powdered form of these plants is more concentrated, they are also more potent.

What Happens if Cats Eat Onions or Garlic?

Cats that eat garlic, onions, leeks, or chives are at risk of developing gastroenteritis. Cats with gastroenteritis make experience such symptoms as vomiting, drooling, diarrhea, stomach cramps, and irritation of their mouths.

A photo of a blue of garlic and an onion.
Avoid letting your cat eat anything that contains onion or garlic. Photo: Caitlin Dempsey.

Symptoms can sometimes take a few days after the cat has eaten onions or garlic to show up. If your cat is vomiting, experiencing diarrhea, appetite loss, or seems listless, they may be experiencing gastroenteritis. Always check with your vet if your cat is experiencing unusual symtoms

Why is Garlic and Onion More Toxic to Cats?

Garlic and onions contain compounds known as n-propyl disulfide and sodium n-propylthiosulfate. These compounds can cause hemolysis, the breakdown of red bloods cells when ingested by cats (and dogs).

Cats and dogs can be adversely affected when eating as little as 0.5% of their body weight in onions. Eating a higher amount of onions eating at one sitting or spread out over a few days can result in the cat developing hemolytic anemia.

Hemolytic anemia is a condition where red blood cells are destroyed faster than they can be made.

Avoid Offering Your Cat Anything Made with Onions or Garlic

Why it may be tempting to offer your begging cat some of your dinner, avoid doing so if that dish has been made with garlic, onions, leeks, or chives. Remember, even small amounts of garlic can harm your cat.

Be careful to check ingredients in any prepared for you may offer your cat. Baby food, which is sometimes offered to sick cats to stimulate their appetite, can have onion or garlic added for flavoring.

So, make sure you keep any source of garlic and onion away from your cat for the sake of their health.


Kovalkovičová, N., Šutiaková, I., Pistl, J., & Šutiak, V. (2009). Some food toxic for pets. Interdisciplinary toxicology2 (3), 169. doi: 10.2478/v10102-009-0012-4

Salgado, B. S., Monteiro, L. N., & Rocha, N. S. (2011). Allium species poisoning in dogs and cats. Journal of Venomous Animals and Toxins including Tropical Diseases17 (1), 4-11. https://doi.org/10.1590/S1678-91992011000100002


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About the author
Caitlin Dempsey
Caitlin Dempsey holds both a master's in Geography from UCLA and a Master of Library and Information Science. She is the editor of Geographyrealm.com and an avid researcher of geography and feline topics. A lifelong cat owner, Caitlin currently has three rescued cats: an orange tabby, a gray tabby, and a black cat.