My Dog Ate a Small Piece of Onion, Will He Be Okay?

My dog ate onions, what to do?

Onions and other allium species foods, such as garlic, leek, scallion, etc. are toxic to your dogs as they damage the blood cells. So, even if your dog has eaten a small piece of onion it’s best to visit your vet and receive a proper treatment. Onion poison cases that are left untreated can lead to serious health problems for your furry friends. 

Are Onions Safe for Dogs?

Onions are toxic to dogs because they contain a certain chemical called n-propyl disulfide. This chemical causes oxidative damage in your pup’s blood cells, meaning it breaks down blood cells and blocks the molecule that carries oxygen to the body. 

This results in anemia and other serious complications. Anemia makes the heart work harder and causes heart diseases such as an enlarged heart or heart failure. Other consequences of onion poisoning include dermatitis, asthmatic attacks, liver damage, and even death.

🐶 Fur Fact: The red blood cells in dogs and cats have low antioxidant capacity compared to humans. That’s why we are not affected by the oxidative process of onions. 

Onions and Similar Foods

The same toxicity levels can be found in any form or type of onion, whether raw, cooked, or powder. This means if your dog ate a delicious meatloaf or a quiche that contains onions is at risk of poison as well. 

Other food varieties part of the allium species are also toxic for dogs for the same reason, including

  • Garlic– It is considered the most toxic of the group, 5 times worse than onions
  • Scallion
  • Leek
  • Shallots
  • Chives
allium foods: garlic, scallion, shallots,onions, etc

How Much Onion is Considered Toxic in Dogs?

The toxicity levels depend on the dog’s size and how much they eat. Generally, it doesn’t represent a risk if your dog has consumed up to 0.5% of their body weight in onions. That is ¼ of a cup for a 20 lb small dog or 1 cup for an 80 lb. labrador, for example.

Symptoms of Onion Poisoning

The first signs you will notice are related to an upset GI– that is vomiting, diarrhea, or drooling. After the onions have been absorbed into the bloodstream, anemia symptoms may appear, but this can take between 1 and 7 days. Signs include pale gums, weakness and lethargy, rapid heart and respiration rates, loss of appetite, brownish or reddish pee color, and collapse. 

Small amounts of onions may not show any immediate signs, however, the toxicity levels can accumulate over time in your dog’s body, and bring serious consequences. 

Onion Poison Treatment

If your dog has eaten the onion in the last hour or so, it means the problem is still in the gastrointestinal (GI) system. In such cases, the vet will induce vomiting to remove any leftover onions from the stomach. This procedure should only be performed by a veterinarian to ensure it is done safely and efficiently. The vet will then administer activated charcoal to bind any remaining toxins in the gut that may have been absorbed. This will help prevent further complications.

However, if the onion has already been absorbed and the toxin has reached the bloodstream, there is no antidote available. The dog will require daily monitoring through blood lab tests, control of anemia, and a diet high in iron to support recovery. In severe cases, a blood transfusion may be necessary.

Important! Call your vet or Animal Poison Control Center (888-426-4435) immediately for advise.

How to Prevent Onion Poison

  • Avoid feeding your dog with food scraps
  • Secure the garbage bags
  • Check the list of ingredients before feeding your dog
  • Keep them out of reach in the kitchen
  • If you have allium species in your garden, restrict the access to your dog

Final Thoughts

If your furry friend happens to eat onions, don’t fret! It’s best to act quickly to ensure his safety. Give your vet a call and schedule an emergency appointment. Acting fast can help prevent any potential complications, so don’t hesitate to reach out for help.


How much onion is toxic to a 10 lb dog?

It is considered toxic when a dog eats more than 0.5% of his body weight in onion. For a 10 lb dog, that is 20 grams of onion or 4 tbsp.  

Can dogs smell onions?

The smell itself shouldn’t hurt your dog. Most dogs won’t even like the smell but it’s best to avoid it because you never know when your dog is going to try new flavors. 

How to treat onion poisoning in dogs at home?

You shouldn’t try to treat onion poisoning at home. Contact your vet as soon as you realize that your dog has eaten it. Your vet can quickly intervene to prevent the absorption of the toxicity or monitor the progression of the anemia.


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Katherine Ortega

Blogger and pet lover. I've been around dogs my whole life and have experience caring for all types, sizes and ages of pups. Senior dogs hold a special place in my heart 💗

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