There is a chemical in chocolate called Theobromine, it is the chemical that gives humans a "happy", but it is poisonous to dogs and cats. Different species are sensitive to different things, some animals can eat things that would kill humans outright and many things humans can safely eat are toxic to some animals
I never really thought about that. My dogs have eaten Oreos, half of a Snickers, and three or four chocolate chip cookies. It's been like a week or two since the last time they've ate chocolate, and nothing's happened. I think it's just a myth or something.
asked a veterinarian this same quest. Chocolate does affect the nervous system, but it depends on the type of chocolate ( milk choc. or dark choc.) the amount eaten, and the size of the dog. Dark chocolate is the most dangerous, large dogs have to eat more than small dogs to be affected. A small amount of dark chocolate will kill a large dog!
Chocolate contains a class of chemicals called Methylxanthines. Chemicals of this type are also found in coffee and many teas. Methylxanthines cause increased heart rate, altered blood pressure, and other circulatory side effects. Humans are larger than dogs, and we have a slower metabolism. "X" amount of Methylxanthines will have "Y" effect on a human over a period of time. "X" amount of Methylxanthines will have "7y" effect on the dog, however, because it is more concentrated in the dog's body and the effect happens faster due to the dog's faster digestion and faster metabolism. There is no gaurantee that a dog will die from a candy bar...people that I know have had chocolate go missing a time or two before with only the dog around. However, a large enough dose will KILL your pet (heart attack) or cause lasting circulatory problems...why risk it?