Hi. Other than having black stools for a little while, nothing much else will happen to your dog. Charcoal will not hurt them, and in fact, some dog treats (little bones or biscuits) are black, because they are charcoal-flavored. Dogs seem to like the taste for some reason, but it won't hurt them. Hospitals (both human and veterinary) sometimes administer liquid charcoal if a child/adult or animal has been poisoned, accidentally overdosed, or ingested certain dangerous chemicals. People don't care for the taste, but dogs aren't that picky (as you have already found out....LOL) If you are still concerned, though, call your vet or just bring your pup in to have him/her checked over to be sure. Good luck!!