How toxic are onions to dogs

Onions, garlic, leeks, scallions – we love adding all of these into our culinary masterpieces for their aromatic and flavor-enhancing properties. However, this family of plants is the most toxic for our dogs. Even a small amount can leave our canine companions in perilous conditions and potentially cause death.

Let’s take a deeper look at onions and find out why they’re so dangerous for our dogs.

The Onion

Onions are members of the allium family of root vegetables. Garlic, leeks, scallions (or green onions), shallots, and chives are as well. 

All onions – white, yellow, green – can cause onion toxicosis in your dog. Whether they are cooked or raw, all parts of the onion, including the leaves, flesh, skin, and juice, are dangerous for your dog.

The ASPCA notes that dogs of Japanese descent – Akita and Shiba Inu – are most susceptible to onion toxicosis. 

Here’s what happens if your dog eats onion

The organic compound in onions causing onion toxicity is called n-propyl disulfide. It damages red blood cells and leads to hemolytic anemia. 

Here’s how it happens:

N-propyl disulfide is a sulfur compound found in all parts of plants from the allium family. Dogs don’t have the enzyme capable of digesting it. That’s all fine, and you’d think they would just poop it out right? Nope, this is a toxic little compound as soon as it enters  your dog’s body.

This sulfur compound attaches to the dog’s red blood cells, specifically hemoglobin, which is the oxygen carrying protein in blood. When that happens, the red blood cells suffer oxidative damage, making them unable to carry oxygen throughout the body properly. They actually form clumps called heinz bodies, which is the telltale sign on a blood smear (under the microscope, it looks like a purple blob on the red blood cells) for onion poisoning.

Inside your dog’s body, a battle begins. Their bodies look at Heinz bodies as invaders, and fight to destroy them. Keep in mind, these are the red blood cells that are now considered the enemy. This process is called hemolysis, or the destruction of red blood cells.

If left unchecked, the battle rages on. The red blood cells are being destroyed faster than the body can produce them, and those produced have decreased lifespans. Your dog’s body can’t get the amount of oxygen it needs to maintain organ or system functions, and everything quickly snowballs into a severe anemic state.

Symptoms can start quickly, but most commonly appear a few days after ingestion. Symptoms of onion toxicity are:

• Lethargy
• Abdominal pain
• Decreased stamina or even fainting after or during exercise
• Loss of appetite
• Pale gums
• Elevated heart rate or respiratory rates
• Vomiting
• Diarrhea
• Loss of coordination (ataxia)
• Discolored urine

If medical care is delayed, kidney failure or death can occur. 

Is there any amount of onions that’s safe for dogs? Short answer: No.

If your dog gets into the onions one day and chows down, it only takes .05% of their body weight in onions to be a toxic amount. For a 45 pound dog, that’s one small onion. Think about what that means for a tiny Yorkie!

The truly frightening fact about Hemolytic Anemia is that it can build up in the blood slowly, over a long period of time. 

Imagine if you have egg bites or quiche every morning for breakfast and there are onions or onion powder in them, and you give your dog a small bite every morning. Then for lunch you have a hamburger (the raw or grilled onions leave their juices on the bun and the burge), and your dog steals a bite. For dinner, you have onion rings, or sauteed mushrooms and onions with your steak, and offer a piece of that steak to your dog. The toxicity builds up in his system. Eventually, symptoms of onion toxicosis will develop.

With any amount of onion, and especially with onion powder and garlic powder, which are more potent than the actual onion , time is of the essence when you see symptoms. Also note that garlic powder and garlic are more toxic than onions, so avoid giving any amount to your dog. 

How is onion poisoning treated?

If you suspect your dog ate onions, or even a part of one, they need to receive veterinary care immediately! Remember that time is of the essence with the ingestion of onions.

Diagnosis: 

The vet will order a urinalysis to check for increased hemoglobin in the urine, and blood work to look for Heinz bodies on the red blood cells. If you have questions, the ASPCA Animal Poison Control Helpline is available 24/7 to assist you.

Treatment:

Vomiting may be induced if onions were ingested recently. There could also be a stomach flush to remove any toxic, undigested portions. 

They may administer activated charcoal to absorb toxins in the gut.

IV fluids will flush the bloodstream and maintain hydration.

Severe cases may require supplemental oxygen and blood transfusions.

Prognosis:

Your dog will spend some time at the vet clinic being closely observed until the crisis is over. Most dogs will be just fine after a mild case of onion poisoning, but the more severe cases could cause a long recovery time.

Pet insurance can be helpful during times like these, allowing you to focus on the health of your pup with less worry about the vet costs. Pumpkin understands this, offering “Best In Show” pet insurance to give you peace of mind when your dog needs medical care.

It’s interesting to note that cats are more likely to suffer from onion toxicosis than dogs. There was a spike in toxicity from onions in cats a few years ago. Vets often use baby foods to entice cats, who have gone off food, to eat. They discovered that onion powder was present in the baby food, causing the issue. Thankfully, baby food now no longer contains onion powder. 

The bottom line for dogs and onions

Whether your meal contains raw onions, dehydrated onions, onion powder, onion juice, fresh or cooked onions of any type (yellow, green, white, etc.), it is dangerous for your dog to eat any of them. Since it can build up in their blood over time, even a tiny amount, given regularly, is cause for great concern and could spell severe anemia and even death for your beloved canine buddy.

There is no safe amount of onion for your dog, and the size, age, breed, and health determine the toxicity levels. Large dogs may get away with a small amount of onion better than a small dog. But we should NEVER give our dogs onions in any form, including any human food containing onions. It’s that simple—onions, or any member of the allium family, may be okay for us dog parents, but they’re an absolute NO for dogs.

When onions and garlic are ingested in large or chronic amounts, it results in Heinz body formation and anemia. Cats are more sensitive than dogs to Allium toxicosis. Clinical signs are generally secondary to the anemia, with resultant weakness, lethargy and pale mucous membranes. Avoid using onion or garlic powder chronically in pet food, and make sure your pet doesn’t ingest large amounts!

What it’s in:

The small amount of garlic sometimes found in dog treats is unlikely to be harmful to dogs. However, if cats or dogs ingest a tasty pan of sautéed onions, garlic, or leeks, poisoning may result. The ingestion of large numbers of garlic pills or powder may also cause poisoning. Garlic was once thought of as a “home remedy” for flea infestations; however, it has been shown to be ineffective and is not recommended by Pet Poison Helpline.

Threat to pets:

These vegetables can cause red blood cell destruction (specifically, Heinz body formation) and result in anemia.

Signs:

Onion/garlic smell on breath, lethargy, pale mucus membranes (due to anemia), tachypnea (elevated respiratory rate), tachycardia (elevated heart rate), vomiting, and a reduced appetite. Rarely, hypoglycemia (low blood sugar).

Treatment:

Induce vomiting and give activated charcoal to decontaminate. Check a PCV (packed cell volume) or blood smears daily to evaluate anemia, blood transfusions if severe anemia. Intravenous dextrose (sugar) if needed.

Prognosis:

Excellent with early intervention and appropriate care.

Onion toxicity is a real concern and can dramatically affect the health of your dog. If you think your dog has eaten any sort of onions (including foods in the same family e.g chives, leeks, shallots, garlic etc.), whether cooked, raw, powdered etc. consult a veterinary professional.

ARE ONIONS TOXIC TO DOGS?

Yes, onions are toxic to dogs, avoid feeding your dog onions.

Onions contain a toxin called N-propyl disulphide which is known to cause a breakdown of red blood cells in your dog resulting in anaemia. They also contain a substance called thiosulfate which dogs can’t digest and organosulfur which results in toxicosis. Ingesting onions could lead to not only anaemia (and haemolytic anaemia) but also liver damage, diarrhoea, vomiting, weakness, dermatitis and asthmatic attacks.

CAN DOGS EAT ONIONS?

In short, no. All parts of the onion, including powders and leaves, are toxic to dogs. This also includes veg that’s part of the allium family such as garlic, shallots, chives and leeks. Just like grapes, you should avoid onions no matter what, cooking onions doesn’t remove any of the toxicity and make sure any broth (including pre-made broth) doesn’t include onions.

CAN DOGS EAT COOKED ONIONS?

No. Avoid cooked onions or any processed onions. Onion juice, powder and broth are still as harmful as raw onions.

SYMPTOMS OF EATING ONIONS AS A DOG

Symptoms can vary depending on the number of onions eaten by the dog, the size of the dog and how quickly the onions were eaten. If a small dog eating a lot of onions very quickly will have more severe symptoms than a large dog eating a small number of onions slower.

These symptoms could range from lethargy, pale gums, weakness, fainting, increased heart rate, decreased appetite, and even reddish urine.

If you see any of these consult a vet immediately. Even if you don’t see these it is always a good idea to visit your vet and have a check-up.

WHAT SHOULD YOU DO IF YOUR DOG ATE ONIONS?

Consult your vet. It’s much better to be on the safe side of things and a vet will be able to catch these symptoms and treat accordingly much better than you can at home. Make sure you keep all onions away from your dog so they can’t eat any more and cause more harm as they’ll definitely try to.

Possible treatments from a vet include carrying out gastric lavage, flushing the stomach or inducing vomiting. If there’s a skin infection bathing may be necessary too. We can’t stress enough the importance of getting a vet’s opinion on this as each individual case will differ.

Your dog will be much happier with a delicious, and also nutritious meal, such as Pure, rather than a plate full of nasty onions. Pure is complete and balanced, tailored to your dog and totally natural with extra vitamins and minerals to ensure your dog gets every bit of goodness they need in their daily life.

Written by: Dr Andrew Miller MRCVS

Andy graduated from Bristol University in 2010 and sees nutrition as a foundation for our pet's wellbeing and takes a common-sense approach. We are what we eat, and it shouldn't be any different for our pets.