Is it normal for dogs to spin around and bite their tails?

When a dog bites its tail, the tail is not far enough from the mouth so it appears to spin in this way. The dog may suddenly go to bite the tail because there is something in the tail, such as an itch caused by a skin disease, or a pain caused by a mosquito bite. At this point the owner needs to see if there is any redness in the area of the bite, or if there are ticks and fleas.