It is fine if you keep a dog as a pet, but if you are offering a chocolate to dog, then you are also harming it. Though chocolate may not be as poisonous as cyanide, large quantities of it will definitely harm dogs.
Chocolate can be lethal to dogs. It consists of Theo bromine, a stimulant found in cocoa beans which is harmful to the animal. Both dogs and horses are affected by Theo bromine. It should not be confused with caffeine. Theo bromine acts as a booster in horses, and hence is banned to be used for horses in horse races. Unlike dogs, horses can tolerate Theo bromine to some extent, as they are bigger animals.
A small of piece of chocolate may not show a very intense response in the animal. If it eats anything else when it has already taken in a large amount of chocolate, then the dog’s system tries to remove this chemical as it can cause damage. The process of cleansing can be done by vomiting and diarrhea. The dog might also cry, breathe rapidly and pass urine excessively. These might be primary symptoms and just a warning, and the dog may not die immediately, but if it is not medically treated the dog may die.
The lethal dose of Theo bromine in dogs may differ depending on size of the dog, and type of chocolate. It was found that 8 ounces of milk chocolate and 4 ounces of baking chocolate are lethal for large dogs. Theo bromine does not completely leave the dog’s system as its half life period is 17.5 hours. Every 17.5 hours, half of the amount gets degraded. In another 17.5 hours half of the existing amount gets degraded. Like that it goes on, and it will never become zero.