Shar-pei looking at onion.

Can Dogs Eat Onion? Fact Checked By Our Vet

Written By Eloisa Thomas | Canine Coach, Double M.A in Anthropology.
Edited & Fact Checked By Renae Soppe | B.A Journalism & Science. 
Last Updated: 11th January 2024

Should your dog eat onion? What happens if your dog ate onion from the garden? Some kitchen staples are poisonous to dogs, but are onions included on the dangerous list? Here’s everything you need to know about it.


Are Onions Safe For Dogs?

No.

Onions are part of the Allium family, a common kitchen ingredient that unfortunately is quite toxic to many animals. Allium toxicity has been abundantly reported by the veterinarian community [1,2] after eating plants from this family, including onions.

Related: What Vegetables Can Dogs Eat?

According to MSD Veterinary manual [2], serious poisoning only happens when a dog consumes 0.5% of their weight in alliums. This means young puppies and small breeds have a higher poisoning risk due to their size and natural fragility. Senior dogs with compromised liver or kidneys tend to be more at risk of allium poisoning.

Due to these risks, onions and other plants in the Allium family are not considered safe plants for dogs. Both onion bulbs and the rest of the plant are toxic, so home gardeners should exercise caution when planting alliums in the landscape.

PRO TIP: If you like gardening, make sure to correct your dog if you ever see them munching on your plants. By redirecting this behaviour early on, you’ll drastically reduce poisoning chances.


Why Are Onions Toxic For Dogs?

Onions, and other plants in the Allium family, are rich in compounds called “organosulfoxides”. These highly fragrant chemicals make them great for –human- cooking, but are at the root of onion poisoning in dogs and other animals.

As organosulfoxides are absorbed by a dog’s intestine, they are metabolised through an oxidation process. Dogs’ physiology isn’t equipped to deal with these highly reactive oxidants, which quickly accumulate in blood cells and causes anaemia.

Related: The Best Vegetables For Dogs.

Among dogs, Allium toxicoses appears as haemolytic anaemia. If left untreated, this causes the body to start destroying its red blood cells which can lead to cardiac arrhythmia, pulmonary insufficiency and eventually death.

Symptoms start appearing up to 2 days after ingestion, and a dog’s condition can quickly deteriorate from there. If you think your dog ate onion, take them to the vet as soon as possible!


How Much Onion Will Cause Poisoning In Dogs?

According to DVM Veronica Higgins for PetMD, consuming as little as 0.5% can lead to onion poisoning in dogs [3]. The specific amount needed to be life-threatening will depend on your dog’s size, weight, and general health. Nevertheless, here are some rough guidelines:

  • Small dogs (less than 4kg): 1/10th of a medium-sized onion or a third of a teaspoon of onion powder.
  • Medium dogs (5kg to 13kg): 1 teaspoon of onion powder or a third of a medium-sized onion.
  • Large dogs (14+ kg): Half of a medium-sized onion or 2 teaspoons of onion powder.

Other factors might increase your dog’s risk. For example, dogs that already have anaemia are especially vulnerable to allium poisoning. Specific dog breeds, such as those of Japanese origin (Akita, Shiba Inu), dogs with chronic conditions or those with liver disease are also more prone to developing haemolytic anaemia.


Symptoms Of Allium Toxicoses In Dogs (Onion Poisoning)

If you suspect your dog ate onions, keep an eye out for these common symptoms:

  • Lethargy
  • Lack of appetite
  • Mood changes: sleepiness, lack of interest in play…
  • Gastrointestinal upset: vomiting, diarrhoea, abdominal pain.
  • Pale gums
  • Intolerance to exercise, or refusal to go on their daily walk.
  • Abdominal pain or discomfort.
  • Whining
  • Increased heart rate (panting)
  • Brown or red urine

Although any of these is a hint that something isn’t right with your dog, if your pup ate onions any negative sign constitutes a medical emergency. Take your dog to the vet as soon as possible!


What To Do If Your Dog Ate Onions

Step 1. Stay calm

Your dog knows if you’re stressed out, so stay as calm as possible as you figure things out. In any case, don’t act without advice from a vet.

Veterinarians don’t recommend inducing vomit at home, unless instructed by a medical professional.

Step 2. Figure out how much and what kind they ate

As soon as you realise your dog ate onions, the most important thing is to try and figure out how much. Your vet will need this information to determine your action course. Consider that powdered or dried onion is more dangerous than fresh as it’s easier for your dog to eat more of it.

Step 3. Call your vet and follow their instructions

Once you’ve determined how much they ate, call your vet. This could be an emergency, so make sure you get a hold of a veterinary professional as soon as possible.

A qualified vet will be able to assess your dog’s risk and provide a tailored action plan either at home or at the clinic. Depending on when your dog ate Allium, your vet will either try to induce vomiting or limit poisoning.


Final Thoughts

Onions are one of the few veggies that should be kept away from your dog, but it’s normal for accidents to happen. If your pup got into your harvest or your spice cabinet, you’ll likely have to take a trip to the vet (or two). Fortunately, with proper care, they’ll quickly recover.

Has your dog ever eaten onions or garlic? Let us know in the comments down below!

Are you wondering if your dog can eat other common foods? Check out our full list below:

FAQ

Are all allium plants toxic for dogs?

Yes. Dogs should be kept away from all members of the Allium family, both edible and ornamental varieties. This includes onions of all colours, but also garlic, chives, green onions and leeks.

Can a dog die from eating onion?

If they eat enough of it and don’t get medical attention, then yes, a dog can die from allium poisoning brought on by eating onions. So if your pup had access to onion and ate it, the best option is to take them to the vet ASAP.

References

  1. R. B. Cope. Toxicology brief. Allium species poisoning in dogs and cats. https://dungenessranchpetresort.com/images/vetm0805_562_566.pdf
  2. MSD Veterinary manual. Allium toxicosis in Animals. https://www.msdvetmanual.com/toxicology/food-hazards/allium-spp-toxicosis-in-animals
  3. PetMD. Can dogs eat onions? https://www.petmd.com/dog/nutrition/can-dogs-eat-onions

Eloisa Thomas


Eloisa Thomas is Gentle Dog Trainers Canine Coach & Anthropologist.

With a double master's degree in Anthropology and awarded a Chancellor's International Scholarship to pursue a PhD in History at the University of Warwick (UK), she's well equipped to write well written and factual canine information that will actually help people understand their dogs better.

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