My dog (boxer/beagle mix) has started slobbering. He never used to do this. Is anything wrong?

Sudden drooling in a pet that doesn't usually drool or slobber indicates a problem. The problem can range from to a chipped/cracked tooth or gum infection (the more common reasons), to poisoning or a foreign object lodged in the throat. Try checking your dog's mouth and look to see if you can spot the problem. Maybe there is a splinter or foreign object you can see and easily remove it without hurting the animal. If not, then it's time to visit the vet and diagnose the severity of the condition.