Onion (allium) poisoning in cats and dogs

In North America, there are about 95 species of cultivated/native Allium species (e.g. onion, garlic, scallion, shallot, leek, and chives) plus at least another 80 ornamental species. All these species and the products derived from them (e.g. onion powder, garlic powder, etc.) be it raw, cooked, dehydrated or after spoilage, are toxic to cats and dogs.
All sorts of foods contain onion or garlic, including baby food. You might not realize that your pet is eating onion or garlic in certain “snacks” or table scraps.  While a small amount of garlic can sometimes be found in dog treats it is unlikely to be harmful. However, if cats or dogs ingest a tasty pan of sautéed onions, garlic, or leeks, a large number of garlic pills, or even garlic powder,  poisoning may result.

Consumption of as little as 5 g/kg of onions in cats or 15 to 30 g/kg in dogs will already result in hematologic changes. Ingestions of onions or garlic of more than 0.5% of a dog’s body weight are toxic. For example, this would equate to a 30 lb dog ingesting about 2.5 ounces of onion or garlic. Cats and Japanese breeds of dogs (Akita, Shiba Inu, etc) are even more sensitive to the effects of alliums.

Signs of the poisoning may start within a day if eaten a large amount, but usually, there will be a lag of several days until signs develop. Clinical signs include:

  • Irritation of the mouth
  • Weakness
  • Vomiting
  • Diarrhea
  • Lethargy
  • Abdominal pain
  • Rapid heart rate (tachycardia)
  • Panting (tachypnea)
  • Collapse
  • Pale or bluish gums
  • Discolored urine

The substance contained in alliums that makes them toxic to cats and dogs is known as thiosulfate. Cats and dogs do not have the enzyme that is used to digest this substance. They also contain a compound called organosulfur which results in toxicosis. Another major problem is the development of Hemolytic anemia (Heinz Body Anemia), which is brought about by the destruction of the dog’s red blood cells which leads to a decrease in red blood cell count.

What to do when your pet ingested onions (garlic, leek, etc.)?
Call us at 563-582-8417. If the incident occurred after hours our emergency line will contact Dr. Neumeister for you immediately. Current clients whose pet receive their general healthcare, including vaccinations, here are eligible for Dr. Neumeister’s 24/7 emergency care. Treatment normally involves the inducement of vomiting, maintaining hydration by providing IV fluids, supplemental oxygen therapy, and possible administration of activated charcoal to help absorb toxins and treat allergic reactions. If the dog has symptoms of skin infection a bath and drying might be necessary as well. Blood tests will be needed to see if hemolytic anemia is occurring, in which case the dog will need a blood transfusion.