Pieces of onion, onion powder, or even cooked onion can cause damage to red blood cells which could result in anemia in both dogs and cats. Cats are especially sensitive to toxicity because their liver is missing an enzyme normally found in dogs and humans. The primary toxic component in onions (n-propyl disulfide) is in all members of the onion family to varying degrees. Garlic for example is often used as a natural substitute for flea repellent. Garlic contains a much smaller amount of n-propyl disulfide than onions, however it is still not recommended given the potential for toxicity.
Clinical signs associated with onion poisoning include anemia, hemoglobinuria (the presence of hemoglobin in the urine), vomiting, weakness, and pallor. Treatment of onion poisoning will generally begin by inducing vomiting and feeding activated charcoal, depending on how much time has passed since the onions were ingested. Afterwards, the animal should be monitored for the development of hemolysis (the destruction of red blood cells) and azotemia (a condition in which the patient's blood contains abnormally high amounts of urea, creatnine and other compounds rich in nitrogen). Critical patients may require whole blood transfusions and fluid diuresis.
The best way to avoid food toxicity in pets is to avoid table scraps altogether. However, sometimes our pets find ways of getting food even when we don't want them to. When this happens, it is important to take the right steps early on to avoid a serious medical condition later. If you suspect your pet may have ingested something toxic, you can always call the pet poison helpline at 1-800-213-6680, then call your veterinarian!
