Why Are Onions Toxic to Dogs?
Can dogs eat onions? As a rule of thumb, dogs should only eat dog food. Of course, we all know that, but… every now and then, it happens that our dogs receive (or steal?) human food, some of it possibly containing onions. If this is the case, it is essential to determine how much onion your dog may have ingested, as onions in too large quantities can be toxic for your dog.
Onions are part of the Allium family – along with approximately 95 other species of vegetables. When ingested by a dog, it can cause gastroenteritis (an upset stomach), but in severe cases, it can cause the breaking down of the red blood cells, which can become fatal.
So keep reading to peel back the layers of all your onion-related questions!
How Much Onion Can Make Your Dog Ill?
If you have come here because your dog just ate an onion, then here are the official Pet Poison Centre’s recommendations:
Ingestion of onions or garlic of more than 0.5% of a dog’s body weight is potentially toxic.
That means that a 30-pound dog can ingest a maximum of 2.5 ounces of onion, or a 15kg dog can ingest a maximum of 75 grams of onion. A whole raw onion generally weighs around five ounces or roughly 100 grams.
If you suspect your dog has ingested more than the possible toxic amount of onion, you should immediately call your local emergency veterinarian.
Signs and Symptoms of Onion Toxicity in Canines
Symptoms of onion toxicosis (poisoning) depend on the amount of onion your dog has ingested, the time since it happened, and any other known (or unknown) medical conditions your dog may suffer from.
Early signs of onion poisoning most often include:
- Anorexia (lack of appetite).
- Vomiting and diarrhea.
- Drooling (a sign of nausea).
- Abdominal pain when touched.
- Lack of energy (depressed).
If your dog has ingested a large number of onions, the symptoms can and will progressively worsen, including in emergency symptoms like:
- Elevated heart rate.
- Increased respiration (fast breathing).
- Pale gums (look in your dog’s mouth, the gums should be the same color as your own)
- Blood in the urine due to kidney damage.
If your dog displays any of the above symptoms, it is imperative to call an emergency veterinarian immediately.
What Should You Then Say When Calling the veterinarian?
Sometimes it isn’t easy to distinguish what information you need to say first. The vital thing to say very first is, of course, that your dog ate (what you suspect to be) too much onion. But, besides that, you should remember to mention this:
- How much onion (a rough estimate will be fine – keep in mind a standard onion size.)
- How much time has passed since your dog ate the onion?
- Your dog’s weight (again, a rough estimate will do. It is better to estimate too low in these cases.)
- Your dog’s gender, breed, and any other medical conditions it may have.
That way, your veterinarian will be able to help you much faster to ensure your dog gets on its way to a speedy recovery.
Diagnosing Heinz Body Anemia in Your Dog
When a dog presents in a clinic with possible onion poisoning, it is essential to quickly determine whether it is becoming anemic (not enough red blood cells). One way to determine this quickly is to determine whether Heinz Body Anemia bodies are present in your dog.
To explain this, we need to start at erythrocytes. Erythrocytes are all types of red blood cells. These carry within them hemoglobin. Hemoglobin is a small protein that is responsible for carrying oxygen.
When the hemoglobin becomes exposed to toxic agents, like oxidative agents in onions, they can become “denatured” (damaged), and they lose their ability to function.
When hemoglobin becomes denatured, they are called “Heinz Bodies.” When a blood sample is taken from a dog and then placed under a light microscope, a veterinarian will be able to visualize these abnormal hemoglobin structures as small “lumps” sticking out of the red blood cells. This is how a diagnosis of hemolytic anemia is made.
How is Onion Toxicity Treated in Dogs?
Now to the real important part: How to treat this onion poisoning. If it’s only been a few hours since your dog ate the onion, the first course of action may be to induce vomiting. The induction is done at a veterinary clinic hospital by injecting your dog with a vomiting-inducing drug.
Vomiting isn’t dangerous (especially not compared to onions), but it can be pretty forceful, and a lot will come up – which is, after all, the point of the whole procedure. With a bit of luck, all of the onion will come up, and you and your dog will be able to leave soon after. If some of the onion has already been digested, active charcoal may also be prescribed.
Suppose it’s been more than a few hours, especially if more severe symptoms have started to appear. In that case, a veterinarian will do some blood work to determine whether your dog is suffering from anemia. If red blood cell destruction has begun, the recommended treatment would be to hospitalize the animal.
Treatment in the hospital will most often include intravenous fluids and possible oxygen supplementation. Supplementing the oxygen in the body is done by placing the dog in an oxygen cage where a high amount of oxygen is present in the air. If the anemia is severe, a blood transfusion, possibly repeatedly, may be necessary.
Careful monitoring of the dog’s red blood cell count will be necessary for days after ingestion as the condition can worsen again.
Prognosis depends on the severity of anemia upon presentation in the clinic and how your veterinarian can initiate immediate supportive care.
The Other Dangerous Members of The Allium Family
As we’ve already discussed, the Allium Family contains more than just onions – actually quite a few more! The most important ones to note are the ones that are often being used in food, as you may not even realize they can poison your dog. Other dangerous members include:
So keep an eye out for these when you’re giving your dog leftovers. Especially garlic tends to be a forgotten ingredient because we use it in almost all types of food!
The Ingredients in Onions That Cause Toxicity and What They do
When your dog ingests onions, it may only get a (manageable) upset stomach. Still, the real worry is the risk of your dog developing anemia – a lack of red blood cells (erythrocytes).
Onions contain an oxidative agent within them. These oxidative agents can cause oxidative hemolysis (breaking down) of the red blood cells when within the body. This occurs if the concentration of agents becomes higher than the antioxidant metabolites that work to keep the cells healthy by “detoxifying” the cells constantly.
When oxidative hemolysis starts happening, the membranes around the red blood cells will become “brittle” and then burst. Effectively “killing” the red blood cells. If the killing of the red blood cells becomes too excessive, your dog will start lacking enough to transport oxygen around the body, causing even more damage to the organs and the body as a whole.
That is why an early diagnosis is crucial.
Steps To Prevent Onion Toxicity in Your Furry Friends
The best way to avoid onion toxicosis is to prevent your four-legged best friend from getting its long snout on them. A few key pieces of advice:
- Never give your dog food seasoned with onion, garlic, chives, and leeks.
- Dispose safely of leftovers. Dogs are creative when it comes to stealing food. Make sure to throw out pieces in a lidded bin.
- Keep onions and other Allium family members out of reach. Don’t keep onions in a bowl your dog may be able to reach – some dogs will jump for food!
Sometimes accidents do happen. No dog owner intentionally harms their beloved dog. Some food you may want to be especially aware of when it comes to the amount of onion they contain could include:
- Tomato sauce.
- Leek and potato soup.
Although we humans often love the smell and taste of food containing onions, you should keep it away from our furry friends.
Veggies That Your Pupper CAN Eat!
Now you might be wondering, should I never give my dog any leftovers at all? Well, that’s a difficult question. Most veterinarians recommend that your dog is only fed dog food. That way, you can ensure your dog gets all the nutrients it needs without any risk of toxic food being present. Providing only dog food also helps prevent obesity in dogs!
But, a lot of dog food contains vegetables, and some vegetables are excellent as a healthy snack for your four-legged friend. Some may even be useful as a healthy snack; these include:
- Green beans
Carrots are primarily a fan favorite with many dogs as they can spend plenty of time chewing on them!
What to do if Your Dog is Poisoned With Onions
If you suspect your dog has eaten onions, the essential part is to determine (as accurately as possible) how much it has ingested and how long ago. If you believe your dog has consumed more than 0.5% of its body weight, the next step is to contact your emergency vet as soon as possible.
A quick visit to a veterinarian is the very best way to ensure your best friend gets on its way to a speedy and complete recovery!
Catharina is a Veterinary Medicine student from Uni of Copenhagen. When she isn’t making camp in the library, stuck to the books, she’s also a writer and avid photographer. Capturing everything from buildings to dogs – especially her poodle Bailey is a frequent subject.