Why does my dog chase his tail and then chew on it?
Dogs chase their tails for several reasons. If your veterinarian examines your dog and doesn’t find any fleas or problems with your dog’s anal glands, then you could be dealing with a behaviour problem. It may have started when he was bored and now tail-chasing has become a habit. In some dogs, tail-chasing can be an obsessive-compulsive disorder. In others, it’s a source of attention. Your veterinarian may be able to suggest a good animal behaviourist that can help diagnose and treat the problem.
In the meantime, try not to react when he chases his tail. Laughing or scolding him are forms of attention and this could be what he wants. If there are any incidences that seem to trigger the behaviour, try to get him into a down-stay before he can chase his tail.
These suggestions may help, but some dogs, if they are causing harm to themselves, may need drug therapy in addition to behaviour modification to solve the problem.