Hi Dr. Barchas,
Daniel, Houston, TX
Chocolate is poisonous to dogs. It contains a number of toxic substances. The most notable is a stimulant related to caffeine.
After eating chocolate, a dogs symptoms depend on its size and the type of chocolate consumed. In general, darker chocolate is more toxic than lighter chocolate. Larger dogs can tolerate larger amounts of chocolate than can smaller dogs.
So, a Labrador retriever that consumes a very small amount of milk chocolate may suffer no ill effects, or may act like hes had too much coffee. A toy poodle that gets into dark bakers chocolate may act wired at first as well. Unfortunately, his symptoms may later progress to heart palpitations and even death.
Because of the potential seriousness of chocolate toxicity, any known or suspected ingestion of chocolate, regardless of type of chocolate and breed of dog, warrants immediate veterinary attention.
While were on the subject of toxic foods, cat and dog owners should be aware that grapes and raisins have the potential to cause fatal poisoning in both species. This is a relatively new discovery, and the mechanism of toxicity is not yet fully understood. Cats and dogs should not eat grapes or raisins.
At this point, I presume I do not need to cover the subject of pets consuming chocolate covered raisins.