4 min read


Why Dogs Don't Like Onions



4 min read


Why Dogs Don't Like Onions




Dogs will eat pretty much anything that is not nailed down, and sometimes even things that are nailed down. Dogs also love to eat table scraps and anything you drop on the floor. If you leave out onions, there is a good chance your dog will eat them. Some dogs do like onions. However, onions are toxic to dogs and should never be a part of the canine diet. Whether eaten once in large amounts or in small amounts over an extended period of time, a dog can end up needing extensive medical care from ingesting onions. While onion poisoning is not common, it is serious and all dog owners should be aware of the signs and symptoms as well as seek medical attention.

The Root of the Behavior

Dogs lack the digestive enzymes to break down the thiosulfate in vegetables in the allium family. The allium family includes garlic, chives, leeks, shallots, and onions. The allium vegetables also include N-propyl disulfides that cause a breakdown of red blood cells in dogs. Hemoglobin, the protein found in red blood cells and the mechanism for carrying oxygen in the blood, becomes oxidized by the build-up of thiosulfate and N-propyl disulfides and forms clumps. This makes it harder for the hemoglobin to carry oxygen in the blood. These small clumps are called Heinz bodies, and they decrease the lifespan of the red blood cells and cause anemia. Your dog’s body begins to see the red blood cells as enemies so it attacks and destroys them through a process called hemolysis. This results in hemolytic anemia, also known as Heinz anemia. An anemic dog is a sick dog.

Onions are dangerous in any form, whether they are raw, cooked, hydrolyzed, or in a powder. Symptoms of onion poisoning can vary depending on the size of the dog, the amount he has eaten, and the amount of time it takes him to ingest the onion. Toxicity can show up when a dog has eaten as little as .5 percent of his body weight in onions, which equates to one medium onion for a dog that weighs forty-five pounds. Signs of anemia and onion poisoning can include lethargy, weakness, bluish or pale gums, decreased stamina, and red urine. Hypersalivation (excessive drooling), lack of coordination, and vomiting with diarrhea can also be signs of onion poisoning. These symptoms can come on slowly if your dog has only been eating small amounts of onion over an extended period of time, or suddenly after he ingests a larger portion. It is important to note that if you know your dog has ingested a large amount of onions you need to seek medical attention immediately. Signs of poisoning can take up to three days to present and the longer he goes without treatment the longer, more unpleasant, and more expensive the treatment will be.

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Encouraging the Behavior

Do not ever give your dog onions, or any vegetable in the allium family, under any circumstance. While the gauge of .5 percent of body weight is the limit, each dog’s system is different so you never really know how much is too much until it is too late. The slow accumulation of small amounts of onion in the body is just as dangerous as the ingestion of a large amount all at once. The best way to avoid slowly exposing your dog to onions is to never give him people food. A lot of foods contain onion and onion flavoring that still contains the thiosulfate and N-propyl disulfide that your pup’s body cannot tolerate. Every little bite of pizza, meatloaf made with onion soup mix, and even some flavored tortilla chips can be dangerous. Tomato sauce, Chinese food, and even some baby foods have onions in them as well. Onion is commonly used to flavor a lot of vegetables and other side dishes, and onion powder is used in most restaurants as a flavor enhancer. Packaged goods also often have onion as an ingredient even when you cannot taste it. Best practice is to avoid giving your furry friend table scraps and read all labels before tossing him a taste of whatever it is you are eating.

If you suspect your dog is suffering from onion poisoning or has recently ingested onions, it is important to call your vet immediately. If you feel ingesting small amounts over time has slowly poisoned him, he may need to spend some time in the hospital and could potentially need a blood transfusion or supplementation with activated charcoal. A recent ingestion of an amount the size of a medium onion is also cause for concern. Your vet may have you induce vomiting if the ingestion was less than thirty minutes prior. Longer than that, you will most likely need to bring him in for medical treatment.

Other Solutions and Considerations

Unlike people, dogs do not seem to mind eating the same foods day in and day out. Having his diet spiced up and varied is not necessary. It is best to stay with products created for dogs that are made up of whole foods and minimal ingredients. There are many foods that are not good for dogs and can be toxic, that you need to limit or avoid in order to protect your pooch. These foods include but are not limited to citrus, chocolate, caffeine, avocado, alcohol, grapes and raisins, coconut and coconut oil, most nuts, undercooked meats and eggs, Xylitol, yeast dough, snacks that are high in sodium, and high fat cheese and dairy to name a few.


Dogs may like the taste of onions or foods with onions, but they are toxic and potentially deadly to your pooch. Ingesting onions can lead to anemia, which will affect his quality of life and make it difficult for him to run and play. Onions and onion powders are used in a lot of foods and snacks that you consume on a daily basis. Sharing with your pet may seem kind, but in the end you are doing him a huge disservice. If you suspect he has ingested onions, call your veterinarian immediately. She may have you induce vomiting or bring him in for testing and possible extended care.

By a Black Lab lover Zoe Byer

Published: 03/13/2018, edited: 01/30/2020

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