Onions, garlic, chives, and leeks are of the Allium family, and are poisonous to both dogs and cats. Garlic is considered to be about five times as potent as onions. Certain breeds and species seem to be more sensitive: Japanese breeds of dogs (e.g., Akita, Shiba Inu) and cats. Onion and garlic poisoning results in oxidative damage to the red blood cells (making the red blood cells more likely to rupture) and gastroenteritis (e.g., nausea, oral irritation, drooling, abdominal pain, vomiting, diarrhea). Other clinical signs of anemia may be seen, and include lethargy, pale gums, an elevated heart rate, an increased respiratory rate, weakness, exercise intolerance, and collapse. Onion and garlic poisoning may have a delayed onset, and clinical signs may not be apparent for several days. While minute amounts of these foods in some pets, especially dogs, may be safe, large ingestions can be very toxic.
If you suspect your dog or cat have onion poisoning or garlic poisoning, call your veterinarian or Pet Poison Helpline for treatment recommendations.