Can My Dog Eat Onions?


dog with onions and exclamation point

Next time you want to give your dog a bite of your pizza, you might want to think again. The sauce probably has onion and garlic in it, which are poisonous to your pup.

Since there are a ton of delicious snacks for humans that are made with onions, it’s super important that pet parents are aware of how toxic they are to dogs and why you should never give onions to your pup.

The Dodo spoke to Dr. Travis Davison, a veterinarian at Bluffton Veterinary Hospital in South Carolina, to find out why onions are so bad for dogs and what to do if your dog manages to eat some.

Why are onions bad for dogs?

Onions are part of the allium family, which includes garlic, shallots, chives, leeks and scallions, and all members of this family are poisonous to dogs.

The substance in onions that’s toxic to dogs is called sodium n-propyl thiosulfate. This compound causes a condition known as anemia, which is when red blood cells break down and the body doesn’t produce enough new ones.

All parts of an onion are toxic to dogs, and any form of onion is poisonous, so you shouldn’t give your pup foods containing raw or cooked onion, onion powder or anything else you can think of. Onion powder is especially toxic because it’s so concentrated, so definitely be sure to keep anything with that ingredient away from your dog.

Certain dogs can be more susceptible to onion poisoning, such as:

  • Japanese breeds, such as Akitas and Shiba Inus
  • Dogs who are already anemic
  • Dogs with lupus
  • Puppies, because they don’t start producing new red blood cells until they’re around 6 to 8 weeks old
  • Dogs taking certain types of medications (including heart medicines, blood pressure medicines, blood thinners, immune suppressors, chemotherapy and insulin)

How much onion is bad for dogs?

Studies have shown that eating about 0.5 percent of their body weight in onions causes dogs to get sick. So a 10-pound dog would have to eat about 23 grams of onion, or approximately one-third of a small onion.

But all dogs react differently, so you can’t really predict the exact amount that will make your pup sick. “It is hard to say [how much is toxic],” Dr. Davison told The Dodo. “There generally isn't a defined toxic dose like there is with some medications … Some can only eat a small amount and get sick.” The best way to keep your dog safe is to keep anything with onion in it away from him.

Also keep in mind that giving your dog some of your food every day can make him sick if it has even a little bit of onion in it, since the effects can accumulate over time.

Symptoms of onion poisoning in dogs

Signs of poisoning to watch out for if your dog eats onion include:

Signs of an upset stomach (like vomiting or diarrhea) can show up pretty quickly after eating onion, but other symptoms associated with anemia may take longer, even up to a few days, to appear. So don’t wait for symptoms to show up to take your pup to the vet if you know he ate something containing onion.

What to do if your dog eats onion

In severe cases, onion poisoning can cause anemia, which can be fatal. That’s why it’s so important to take your dog to the vet as soon as you realize he ate something with onion, even if it was only a little bit or if symptoms haven’t shown up yet.

“Contact your vet ASAP,” Dr. Davison said. “They may have you contact an animal poison control center (they will charge a fee, but it's worth it).”

Two phone numbers you should always keep on hand are the ASPCA poison control number, (888) 426-4435, and the Pet Poison Helpline, (888) 426-4435, so you have them at the ready in case of emergency.

Try to give as much information as possible to your vet. This will help them provide the best treatment for your dog and treat him more quickly — and faster treatment will usually lead to a better outcome.

Some important info to give to your vet is what your dog ate, how much he ate and how long ago it was eaten.

“Some things can be fixed very quickly and easily, [but] some require more intensive care — inducing vomiting, IV fluids, medications to manage symptoms, monitoring lab work for blood sugar/organ damage, etc.,” Dr. Davison said.

Treatment for onion poisoning in dogs includes:

  • Inducing vomiting
  • Giving activated charcoal to prevent absorption of the toxins
  • Performing bloodwork to check the red blood cells
  • IV fluids to flush the toxins out of your dog’s system
  • Oxygen or a blood transfusion if the dog has anemia

To keep your pup safe, Dr. Davison’s advice is: “If you're not sure you can feed something to your pet, don't do it. If you do think they ate something and it caused it, just be truthful to your vet!”

So avoid giving your dog anything with onion in it, and if he does manage to eat something that has onion, don’t wait for symptoms to show up to take him to the vet. As long as you get him treatment right away, he’ll most likely be fine.