A dog poses with some onions.

Most of us have the list of common food items dogs should not eat memorized. No chocolate, no grapes or raisins, and no onions. Although we know dogs are not supposed to have these things, we often don’t know why. Why can’t my dog have onions? Why do they get sick?

Onions contain a compound called N-propyl disulphide. This compound binds to a dog’s red blood cells, causing damage. If your dog loses too many red blood cells to this damage, they will become anemic. If enough red blood cells are lost, it can even be fatal.

Onions are considered the most dangerous human food for dogs and should be kept away from your pet even in small amounts.

How Much is Toxic?

Onions are relatively common. If you slipped up and gave your dog spaghetti with a tiny bit of onion in it, should you rush your dog to the vet? The answer depends on the size of your dog, and how much onion they got.

According to PetMD, onion poisoning is most consistently seen in dogs who consume more than 0.5% of their body weight in onions. Some dogs are more prone to onion poisoning than others, most notably Japanese breeds of dog such as the Shiba Inu, and dogs with medical conditions such as Diabetes.

If you are unsure about the amount or your dog’s sensitivity to onions, call your vet or your local pet poison control line. They can help you determine whether the dog needs to see a vet or not.

Symptoms of Onion Poisoning

Symptoms include diarrhea, vomiting, sore abdomen, reduced appetite and dehydration. Since onion poisoning also causes anemia, you may eventually see lethargy and trouble breathing. If you see any of these signs and know your dog has eaten onions, you should take your dog to the vet right away.

All members of the allium family, including green onions, leaks and garlic are toxic to dogs. Every part of the plant is poisonous, including the bulb, leaves and flowers.


If you caught your dog eating onions within hours of it happening, the usual treatment is to induce vomiting. This should be done by your vet only, it is not recommended for you to do it on your own. If it’s too late to induce vomiting, your dog may have to be hospitalized for IV fluids and blood transfusions.

Most of the time, onion poisoning is treatable and death is rare. It’s still better for your pet to avoid eating onions, as even if it doesn’t kill your dog, even a small amount of onions is not healthy for them.

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By Andrea

Andrea is a dedicated dog mom of three chihuahuas. She has over a decade of experience as a dog groomer, chihuahua owner, and more recently as a dog trainer. She loves all things canine, particularly chihuahuas.

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