Why Do Dogs Drag Their Bottoms?

This is a very common question for dog owners. When dogs drag their bottoms on the carpet or outside on the grass, it means that their anal glands are bothering them. The anal sacks are located just inside the dog's rectum. Their purpose is to "mark" their territory with the dog's own special scent.
However, when the anal glands are too full (similiar to what a human feels when constipated), dogs will try to empty them by dragging his/her bottom. Unless dogs drain their anal glands, it causes them pressure and pain.
Part of any dog's yearly check-up with the veterinarian should include emptying his anal glands. In fact, veterinarians can teach dog owners how to do this themselves.  Many groomers do this as a part of their grooming routine as well - ask your groomer to do it at their next bathing session.  It's very easy and will be a great relief to your dog.