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Onions can cause more damage to your dog than just bad breath. This pungent culinary favorite might add flavor to your dishes, but it contains a toxin that can cause serious complications for dogs.

Are Onions Toxic to Dogs?

Yes, onions are toxic to dogs and should not be ingested. Onions contain a toxic principle known as N-propyl disulfide. This compound causes a breakdown of red blood cells, leading to anemia in dogs.

The toxin causes oxidative damage to your dog’s red blood cells by attaching to the oxygen molecules in those cells. This reduces the ability of the red blood cells to carry oxygen and also tricks your dog’s body into thinking that the blood cell is an invader. The red blood cell is destroyed in a process known as hemolysis, resulting in hemolytic anemia.

What Parts of Onions are Toxic to Dogs?

All parts of the onion plant are toxic to dogs, including the flesh, leaves, juice, and processed powders. Whether raw or cooked, fried or powdered, onions and the rest of the allium family, which includes shallots, leeks, chives, and garlic, are harmful to dogs.

Onion powder is in a surprisingly wide range of foods, from soups to baby food. It only takes 100 grams of onion (about the size of a medium onion) per 20 kilograms of a dog’s weight to cause toxic effects, which means that a 45-pound dog would only have to eat one medium-to-large onion to experience dangerous toxicity levels. Since most dogs would happily devour a bag of unattended onion rings or an onion casserole given the opportunity, this is a serious concern.

Three Beagle puppies eating out of a bowl outdoors. Approved by Denise Flaim August 2018. Adobe Stock #191071686
©jarun011 -

Onion and garlic powders are even more potent than fresh onions. It is always a good idea to check the label of any human food we feed to our dogs, and onion powder should be in your list of “don’ts.” As a word of warning to those with multi-species households, onions are even more toxic to cats than they are to dogs, so keep both feline and canine tummies free of onion treats.

Symptoms of Onion Toxicity in Dogs

If you think your dog may have eaten onions, look out for symptoms of anemia, including:

The ASPCA also lists vomiting, elevated heart rate, and panting as signs of onion toxicity in dogs.

If your dog is exhibiting any of these symptoms, the best thing you can do to is get them to a veterinarian as soon as possible. Your veterinarian will diagnose your dog’s condition based on their symptoms and blood work. If your vet detects hemolytic anemia or the formation of Heinz bodies on a blood smear, and that is combined with a recent history of onion exposure, then all signs will point toward onion toxicity.

Other conditions can also cause hemolytic anemia, so it is important to get an accurate diagnosis to ensure your dog gets the best care.

Golden Retriever on an exam table having its heart checked by a vet. Approved by Denise Flaim May 2018. Getty Images #525965743
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Treating Onion Toxicity in Dogs

The most important thing you can do, as a dog owner, to treat and prevent onion toxicity is to never allow your pup to eat onions. If your dog is suffering from toxic effects, they will probably require veterinary attention. Your veterinarian may induce vomiting, in dogs, depending on how recently your dog ate the onions, and will offer supportive care until your dog’s body can produce enough healthy red blood cells to replace the damaged ones. In severe cases, your dog may require a blood transfusion.

Onion toxicity can be fatal. The faster you get your dog to the veterinarian, the better your pup’s chances, and you can prevent onion poisoning from recurring in the future by keeping onion dishes out of the reach of inquisitive noses.

Healthy Vegetables for Dogs

Onions might be a no-go, but there are lots of healthy vegetables that are perfectly safe in small amounts for dogs. Try offering your dog carrots, cucumbers, or green beans as a healthy treat, and along with other fruits and vegetables that are safe for your dog to eat.

Related article: The 8 Biggest Dog Food Myths
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