Why is chocolate so bad for dogs?
Actually, it’s the molecule theobromine that’s found in chocolate that is toxic to dogs. Dogs have a very hard time metabolizing theobromine, as it attacks their central nervous system. Warning signs of theobromine poisoning include high temperature, diarrhea, seizures, vomiting and rapid breathing.
Different types of chocolate contain differing levels of theobromine. Milk chocolate typically only has 60 mg per 1 oz, but dark chocolate has 400 mg per 1 oz.
Source: American Chemical Society