Can Dogs Eat Onions?

Many of us enjoy a pinch of onion flavor in our favorite dishes.

But are they safe for our dogs?

The answer is a hard NO.

Onions rank high on the list of harmful human foods for our furry buddies. Too much onion could harm your dog's red blood cell count, causing hemolytic anemia.

Every bit of the onion is a risk factor—ensure they're stored somewhere your dog will never reach.

Let's uncover more about why onions are harmful to dogs, the signs of onion toxicity, and the steps you should take if such a mishap occurs.

Why are Onions Toxic to Dogs?

Onions contain compounds such as N-propyl disulfide and thiosulfate, both of which dogs cannot properly digest. These substances cause oxidative damage to red blood cells, leading to hemolysis (the rupture of red blood cells). 

Once red blood cells are compromised, the body is unable to carry oxygen effectively, which may result in hemolytic anemia. This dangerous condition can cause fatigue, weakness, organ stress, or even organ failure in severe cases.

It doesn’t matter if the onion is raw, cooked, dehydrated, or powdered—all forms are toxic to dogs. Even small amounts, especially when eaten repeatedly, can build up and cause serious long-term health problems.

Is the Whole Onion Unhealthy for Dogs?

When we say that every single part of the onion is harmful to dogs, we mean every. single. part.

Think of an onion as a toxic cake. Whatever slice you take, from top to bottom, inside or out, it's all bad news for our four-legged friends. Whether it's the juicy flesh, the crunchy leaves, or even that oniony smell we sometimes get, all these parts contain toxic chemicals that our dogs must avoid. That includes onion juice or the onion powder we use in the kitchen (which is more pervasive than you'd imagine!).

Your dog doesn’t need to eat a pile of onions to get sick, just a small amount can be harmful. Toxicity begins at about 15–30 g per kilogram of body weight, meaning that for an average 45-pound dog, even a single medium onion could be enough to cause poisoning.

Can Dogs Eat Cooked Onions?

Don't get tricked into thinking cooking the onion makes it any safer for your pup.

Whether fried as crispy onion rings, dehydrated in our favorite soups or even added to baby food, onions still cross into the danger zone for dogs. That's right, even baby food! Always double-check the ingredients, especially if you have little kiddos munching away and a curious puppy nearby.

How Much Onion Will Make My Dog Sick?

There isn't a magic number or specific amount of onions that spells trouble for a dog.

For starters, it's about the size of a dog. A large dog might tolerate more than a tiny pup, although it's not a risk you'd want to take.

Then there's the breed of the dog. Some dogs, particularly Japanese breeds like Akitas and Shiba Inus, are more prone to onion poisoning due to genetic differences in their red blood cells. These differences make their cells more fragile and less able to withstand the oxidative damage caused by onion compounds, increasing their risk of toxicity.

If your dog is the curious type that munches on wild onions outside, that's a red flag! Gulping down multiple onions at once will cause sudden health problems, like hemolytic anemia, in just a few days.

Small onion snacks can be just as destructive over time. Imagine your dog sneaking a tiny bit of onion every day. Over time, these bits will add up, causing health issues. It's like eating one chip every day and then being shocked when you find out you've gone through the whole bag in a month. 

Symptoms of Onion Poisoning in Dogs

Onion toxicity doesn’t always show up right away; symptoms can appear within 24 hours or may take several days as red blood cells begin to break down.

Key signs to watch for include:

• Weakness, lethargy, or sudden collapse.
• Loss of appetite.
• Vomiting and diarrhea (sometimes with a strong onion odor).
• Pale or discolored gums.
• Panting or elevated heart rate.
• Excessive drooling or mouth irritation.
• Dark or reddish urine (a sign of hemolysis).

These symptoms occur because onions damage your dog’s red blood cells, reducing their ability to carry oxygen. In severe cases, this can lead to hemolytic anemia, which puts stress on the liver, heart, and other organs.

If you know your dog has eaten onions, or even suspect it, contact your veterinarian immediately. Early treatment can prevent serious complications.

If Onions are Toxic to Dogs, is Garlic, Too?

First off, let's get to know the family tree a bit. Onions and garlic both come from the Allium family. It's like they're cousins! This family also includes scallions, shallots, leeks, and chives. Because garlic and onions are closely related, many people assume they’re equally dangerous to dogs. 

 

The key difference is that onions are toxic in any form and amount, while garlic is dose-dependent; measured amounts may be tolerated.

 

Garlic stands out in its group as the harmless member to dogs, unless consumed in very large amounts. When fed in appropriate quantities, uncooked fresh garlic offers numerous health advantages for your canine companion!

 

But the absolute superstar in garlic is allicin. Whenever you chop or crush garlic, you awaken an enzyme that teams up with a protein, and BOOM! They create allicin, which has a bunch of health benefits for dogs.

 

So, while onions and some of their Allium family members are nothing but trouble for dogs, garlic isn't in the same boat.

Onion Poisoning Diagnosis

Your fur baby had a sneaky snack, and you're worried it might have been onions or something with onions in it. Naturally, you're thinking, "Okay, what now?"

First stop? The vet's office.

Your vet will likely start with a blood test to determine how onion toxicity affects your dog's blood.

Next, they will conduct a urinalysis to determine if there are traces of hemoglobin in the urine (which shouldn't normally be there).

Lastly, if your dog has recently pooped or thrown up, the vet might look for any bits of onion hiding there.

What Dog Parents Can Do about Onion Poisoning

First and foremost, switch into action mode. If you catch your dog gobbling down onions or even think they might have, it's time for veterinary care.

One remedy your vet might use to cleanse your dog's stomach is activated charcoal. Think of it like a sponge soaking up the onion contents in your dog's belly. If you have activated charcoal in a first aid kit, it can be given under professional guidance. The wrong dose or timing can do more harm than good, so always consult your vet before using it.

Ingested activated charcoal binds to GI tract toxins, preventing their absorption into the body. This makes activated charcoal an ideal treatment for dogs that have ingested poison or toxins. However, activated charcoal is not a cure-all; it just buys some time.

Next, the vet might give your dog some fluids, check if their liver was affected, or resort to blood transfusion in severe situations. Sometimes, the vet might hook your dog up with oxygen supplementation if the red blood cells have difficulty carrying oxygen. They might even keep your dog overnight for monitoring.

FAQ: Onion Toxicity

Are chives safe for dogs?

No. Chives belong to the same Allium family as onions, and they carry the same risks of poisoning.

What if my dog only ate a small piece of onion?

Even small amounts can be harmful, especially to smaller breeds. While one small bite may not cause immediate illness, repeated exposure or larger portions can lead to serious health problems. Always consult a veterinarian if ingestion occurs.

How can I prevent accidental onion poisoning?

Avoid feeding table scraps that contain onion, keep trash cans secure, and check ingredient lists for onion powder or undisclosed ‘spices’, commonly found in soups, broths, sauces, and even some dog treats.

Keep Your Dog Safe with Smarter Nutrition from Volhard!

Fortunately, if the onion snacking is caught early, most dogs return to their tail-wagging, ball-chasing selves in no time!

For more advice on dog nutrition, health, and training, contact us and check out our other blogs, too!

Volhard Dog Nutrition and its expert canine nutrition coaches offer online consultations to help more dog parents discover why and how to feed their dogs the healthiest foods!

Speaking to a Volhard canine nutrition coach will help you understand the inseparable relationship between healthy food, a healthy body, and a healthy mind.

If you want to contact one of our Volhard canine nutrition coaches, you can do so by utilizing our Live Chat feature or scheduling a consultation.

Reference List

1. Beynen, A. C. (2020). Onion in canned dog food. ResearchGate. Retrieved from https://www.researchgate.net/publication/341668930_Beynen_AC_2020_Onion_in_canned_dog_food
2. Guitart, R., Croubels, S., Caloni, F., & Davanzo, F. (2008). Heinz body anaemia in two dogs after Catalan spring onion (calçot) ingestion: A case report. Veterinární Medicína, 53(7), 411–415. Retrieved from https://vetmed.agriculturejournals.cz/artkey/vet-200807-0006_heinz-body-anaemia-in-two-dogs-after-catalan-spring-onion-calcot-ingestion-a-case-report.php 
3. Harvey, J. W., & Rackear, D. (1985). Experimental onion-induced hemolytic anemia in dogs. Veterinary Pathology, 22(4), 387–392. doi:10.1177/030098588502200501. Retrieved from https://pubmed.ncbi.nlm.nih.gov/4035943/ 
4. Kovalkovičová, N., Sutiaková, I., Pistl, J., & Sutiak, V. (2009). Some food toxic for pets. Interdisciplinary Toxicology, 2(3), 169–176. doi:10.2478/v10102-009-0015-y. Retrieved from https://pmc.ncbi.nlm.nih.gov/articles/PMC2984110/ 
5. Merck Veterinary Manual. (n.d.). Garlic and onion (Allium spp.) toxicosis in animals. Merck Veterinary Manual. Retrieved from https://www.merckvetmanual.com/toxicology/food-hazards/garlic-and-onion-allium-spp-toxicosis-in-animals
6. PetMD. (2022). Can dogs eat onions? PetMD. Retrieved from https://www.petmd.com/dog/nutrition/can-dogs-eat-onions
7. 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 Diseases, 17(1), 4–11. doi:10.1590/S1678-91992011000100002. Retrieved from https://www.researchgate.net/publication/278718392_Allium_species_poisoning_in_dogs_and_cats

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