To dogs, some of the most toxic forms of chocolate are cocoa powder and cooking chocolate. A medium size dog of around 10-kilograms can be seriously affected if it eats even one-fourth of a 250gm packet of cocoa powder or half of a 250gm block of cooking chocolate. The reason is that these forms of chocolate contain 10 times as much of the ingredient theobromine than does milk chocolate. So, one of our favorite foods, the popular chocolate mud cake could be a real health risk for a small dog. Just by licking a substantial portion of the chocolate icing from a cake can make a dog very ill. After cocoa and cooking chocolate, semi-sweet chocolate and dark chocolate forms are also to be avoided. Milk chocolate is the least dangerous. The safest thing to keep in mind is that all forms of chocolate are on the no-no list as we want only the best dog food for our pets.