Can Cats Eat Green Onions?

Can Cats Eat Green Onions?

Right beside my house, I have wild green onions growing. I don’t use them much because no one in my house likes them (they make myself and my oldest kid sick and no one else cares), but they do make for some nice purple flowering in the early spring and they help to repel insects, so they get left alone. But once in a while, the cats go outside too and chew on the grass by the door.

With green onions, otherwise known as shallots, growing right nearby, should I be worried about one of them accidentally poisoning themselves? Can cats eat green onions?

Short answer: No. Shallots (green onions) are part of the overall Allium family and they are all very toxic. Good thing my cat has never gone near them!

Do Cats Like Green Onions?

Fortunately, most cats are not remotely interested in eating green onions. There is nothing in them that would attract most felines and they won’t even go after them out of interest to see what you’re up to.

They don’t taste particularly good to cats, they don’t smell particularly good to cats, and given a choice between chewing something that many cats will instinctively know is bad and going after the grass, the grass will win every time.

The main way that cats get into green onions is as a by-product of getting into something else such as pizza, tomato sauce, chive bread, baked potato fixings, and more. But alone, most cats won’t go after green onions which is a good thing considering how toxic they are!

Do Cats Hate Green Onions?

It’s not so much that cats hate green onions, but rather they will simply avoid eating it unless it’s mixed into something else. Cats are generally well attuned to things that are going to make them truly sick and so will usually avoid those foods. The danger comes when green onion is mixed into something else that a cat may eat.

For all that my cat enjoys chewing on the grass by my door, she’s not shown the slightest interest in the green onions. And for that, I’m pretty grateful!

Can Green Onions Kill My Cat?

Green onions can absolutely kill your cat and it doesn’t take much to cause a cat to become incredibly ill and have problems.

The main problem is that any member of the allium genus – including garlic, scallions, and any onion – is that they damage the red blood cells in your cats. Damage to the red blood cells causes anemia and the symptoms don’t necessarily show up right away.

It also doesn’t take much to make a cat sick – since these animals are so small, the dose doesn’t have to be big. In fact, an amount that weighs a mere .5% of your cat’s body weight is enough to cause poisoning.

The reason why this happens is because of the thiosulphate found in green onions. This causes oxidative red blood cell damage and so their ability to carry oxygen drops and symptoms of anemia occur.

Other things that ruin the blood’s ability to carry oxygen are that chives and green onions can relax the heart muscles and dilate blood vessels, leading to low blood pressure and other heart problems. So, it’s simply bad all around.

Symptoms of green onion poisoning include:

  • Drooling
  • Mouth irritation
  • Nausea
  • Stomach discomfort
  • Diarrhea
  • Pale gums
  • Lethargy
  • Skin discoloration
  • Weakness
  • Collapse
  • Blood or orange colored urine
  • Panting
  • Heart rate
  • Wobbly movement

It can take several days for these symptoms to show up, so don’t think you’re in the clear if twenty-four hours has passed after a cat ate some onion and nothing happened.

Symptoms get worse the smaller the cat is, and some breeds (again by size) are more susceptible than others. My big cat might be able to nibble a little and get away with it. The tiny Siamese cross I grew up with would have been poisoned at a taste, most likely because she was so little.

If a cat eats green onions in too high a quantity, it can certainly kill them, though it might not happen right away.

Some cat foods even have levels of alliums in them and while they are at such a low level as to be considered safe for cats, it’s still important to check and maybe change foods as allium can build up in a cat’s body and cause long-term toxicity and damage.

This may also be why some cats are more sensitive to certain foods, so check your ingredients list.

How Many Green Onions are Safe to Feed My Cat?

None. Green onions in any amount are toxic to cats. If you think your cat ate some, it’s important to contact your vet or poison control right away to get help and probably treatment.

Treatment for poisoning generally includes inducing vomiting, the use of activated charcoal and sometimes more extreme measures will be required like IVs to rehydrate a cat that has lost a lot of fluid due to vomiting and diarrhea.Can Cats Eat Green Onions?

Absolutely the best thing to do is to prevent your cat from coming into contact with green onions at all.

Make sure that you don’t let them near any wild-growing plants, keep them out of the kitchen while you’re cooking if you have a particularly curious or insistent cat, and don’t feed them foods that are meant for humans unless you know exactly what’s in them.

Things like garlic and onions sneak into even the most innocuous things like baby food and beef broth! (Trust me on this – I was looking for beef broth to tempt my cat to eat something when she was ill, and they all had garlic in them.) It’s best to simply avoid letting your cat eat anything that’s meant for humans unless you know exactly what went into it.

And cooking green onions does not prevent this from happening. Neither does roasting, baking, dehydrating, or any other way to prepare them. Green onions are, quite simply, toxic to cats in all their forms and there’s nothing you can do to change that.

I’d even recommend taking them off cat food with any sort of allium in them because you just don’t know what the long-term effects will be.


Green onions may be one of the milder of the onion family, but that doesn’t make them any less toxic to cats.

Onions of any sort, and garlic, can cause a lot of damage to your cat’s circulatory system and such damage can be permanent if it goes on too long, shortening your cat’s life and causing other issues. It’s an easy thing to prevent though: don’t let your cat have green onions ever, in any form!

Do you have to fight with your cat to get them to not try to eat your green onions?