If you've ever fed your dog table scraps containing onion, or shared a fried onion with your pet, you could be poisoning him. It doesn't take a lot of onion to cause toxicity in dogs. It occurs more often if the animal eats a large amount at one time or consumes lesser amounts frequently. If you see your dog eating an onion or believe he has consumed some, call your vet immediately.
Any members of the allum family -- onions, garlic, chives or leeks -- are toxic to canines. The form doesn't matter, as fresh or dried members of this family are equally poisonous. The primary culprit is the oxidant n-propyl disulfide, which can cause an immune response in which the dog's body attacks its own red blood cells. While any dog might show symptoms of onion poisoning, canines of Japanese descent appear especially sensitive and prone to more serious side effects. These include the shiba inu, Japanese chin and Akita.
Depending on the amount eaten, onion poisoning symptoms develop within a day or so of consumption, or over a period of weeks. Remember that onion consumption can be cumulative. All sorts of foods contain onion, including baby food. You might not realize that your dog is eating onion or garlic in certain "snacks" or table scraps. Symptoms include vomiting, diarrhea, drooling, rapid breathing and heart rate, abdominal pain, appetite loss, mouth irritation, dark urine, lethargy and pale gums. In a worst case scenario, your dog might collapse from lack of oxygen because of insufficient red blood cells. The dog develops hemolytic anemia, or red blood cell destruction.
If you witnessed your dog eating onions, your vet can induce vomiting if it's within a few hours' time frame. She also can administer activated charcoal to help absorb toxins in the animal's system. If blood tests show that hemolytic anemia is occurring, your dog might need a blood transfusion.
If the onion consumption was ongoing, treatment consists of the obvious -- stop feeding onions -- and supportive care. Keep your dog quiet and comfortable. If his red blood cell count is low, you don't want him to get excited and pass out due to insufficient red blood cell numbers. The good news is that onion toxicity is rarely fatal. Eventually, once the onion is out of the system, the dog's bone marrow starts to release new red blood cells. Most dogs will recover completely from a bout of onion poisoning, as long as they no longer eat products containing onion.