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).
What breed of dogs have killed more people? The Pit bull has killed the most people, surprisingly, as they are so friendly. The second breed that has killed the most people is the Rottweiler.
We have never, in over 50 years, had a dog die that was less than 20. Some have lived well into their 20's. This includes German Shepherds, Chows, Golden Retrievers, Rottweilers, Westies, Border Collies, Dobermans, pit bulls, labradors, etc.