A: Chocolate can be safe to very dangerous for dogs depending on the type, quantity and concentration of stimulants of chocolate that is consumed.
Dogs (and cats) are very sensitive to stimulating chemicals, such as theobromine, which is found in chocolate. Theobromine is a member of the methylxanthine class of chemicals including caffeine, which is the primary methylxanthine found in coffee and soda.
Dogs metabolize theobromine at a slower rate than humans. Therefore, they are more susceptible to toxicity resulting from dietary indiscretion involving chocolate. Gastrointestinal, urogenital, cardiovascular and neurologic systems can be adversely affected. Gastrointestinal signs include vomiting, diarrhea and increased water consumption. Urogenital signs include increased urination or urinary incontinence. Cardiovascular signs include increased heart rate and arrhythmia. Neurologic signs include restlessness, muscle tremors, seizure activity and, in severe cases, death.
The highest concentrations of theobromine are found in baking and dark chocolate. Semisweet and milk chocolate contain less, but still enough for concern. The lowest amounts of theobromine are found in chocolate-flavored commercial products and baked goods. White chocolate contains no theobromine.
Chocolate also contains fat, sugar and other ingredients that can cause vomiting, diarrhea, abdominal discomfort and pancreatitis. In general, my recommendation is to not feed chocolate to your dog and prevent its access to places where such tasty human treats are kept.