Chocolate is toxic to dogs, and owners must take care to keep it away from their pets. It potentially causes serious illness and even death in dogs.
Chocolate is not safe for dogs to consume primarily because of the theobromine it contains. Theobromine is both a central-nervous-system and cardiovascular stimulant, and its half-life in dogs is about 17.5 hours. The human body is able to break down the theobromine much more efficiently than is the body of a dog. While a dog should never be given chocolate, unsweetened chocolate is particularly harmful. The size of the animal and how much chocolate is consumed are also factors in the severity of the reaction. If a dog consumes chocolate, contact a vet immediately.