Generally speaking, toxicity occurs when a dog ingests more than 0.5% of their body weight in onions at one time. To put it simply, even a small amount of onion, garlic, or other toxic allium food can poison a dog easily.
What happens if my dog eats a little bit of onion?
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 your dog's red blood cells.
How much onion will harm a dog?
"Consumption of as little as 15 to 30 g/kg in dogs has resulted in clinically important hematologic changes,” says Hohenhaus. “Onion toxicities are consistently noted in animals that ingest more than 0.5% of their body weight in onions at one time.” So, think that one fourth of a cup can make a 20-pound dog sick.
Will a small amount of cooked onion hurt my dog?
Remember that any part of the onion plant can be toxic, and it is still toxic if cooked (think onion rings, for example). The effects can also accumulate if a dog is fed smaller amounts of onion over a few days. Watch out for onion powder, as this is commonly added to lots of processed foods.
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