Onions Poisoning in Dogs, Symptoms and Treatment

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Many surprising foods like raisins and grapes, yeast in bread dough, and chocolate all pose a risk to dogs. Here is another common human food to add to the list: onions.

Clinical Presentation

When a dog comes into the office with severe respiratory distress, panting heavily and laying down, a laboratory test may show that it has a dangerously low level of red blood cells.

After talking with the owner, it often appears that the problem began after the dog got into the kitchen garbage. In these cases, a blood smear is likely to reveal changes to the shape of the red blood cells consistent with oxidative damage. Diagnosis: an acute toxic reaction to eating onions.

Everyday Toxins

Many owners are not aware that onions and garlic and even some common household chemicals can cause this type of life-threatening reaction in the blood. Tylenol, rat poison, and even the zinc in pennies can cause severe distress from this type of oxidative damage to red blood cells. This is especially common in puppies and the smaller breeds, such as a Maltese, Yorkshire or Jack Russell.

brown German shepherd on roadway beside trees
brown German shepherd on roadway beside trees

Dogs over 20 pounds often consume similar substances, but their larger mass usually prevents such a severe reaction. For this reason, it is important to deduce the overall volume of what was likely ingested by any dog.

Signs of Onion Toxicity

Compounds found in cooked, raw, or dehydrated onions, shallots, scallions, or leeks begin reacting with a dog's metabolism soon after ingestion. Common signs in dogs that have ingested onion include:

  • Lethargy
  • Trouble breathing
  • Vomiting
  • Dark-colored urine
  • Yellowing of gums (icterus) and yellowing in whites of the eyes

Affected red blood cells cannot carry oxygen to the body, so within a few hours, the dog becomes lethargic and has trouble breathing. The dog may also vomit up the onions and the other foods consumed from the trash.

grayscale photo of dog lying on floor
grayscale photo of dog lying on floor
brown and white corgi puppy on brown dirt ground during daytime
brown and white corgi puppy on brown dirt ground during daytime
white and brown long coated dog
white and brown long coated dog

Treatment for Onion Toxicity

After a dog suffering from onion toxicity is brought to the hospital, initial lab tests will usually point to acute anemia as there are changes to the red blood cells that characterize this type of toxic reaction. Depending on the dog's condition, blood replacement therapy may be necessary until the toxic chemicals have been gradually metabolized.

Metabolism of the toxin is rapid in dogs, but the damaged red blood cells may take two to three days to be removed from circulation. Typically, dogs that are monitored closely and receive the right support, including blood transfusion(s) and intravenous fluids, make a quick recovery and can usually go home after one to three days at the hospital.

Possible Complications

It is important to watch the dog for other signs of distress, such as gastritis, diarrhea or pancreatitis, especially when fatty foods from the trash have also been consumed along with the onions.

In any case, knowing what foods or substances and the amount of each that the dog likely ate in the house, from the trash, or in the yard, can help the veterinary specialist determine the nature of the problem and the best way to help the dog recover from the unfortunate ingestion.