Dogs drag their butts primarily because of discomfort or irritation around their anal area. The most common reason is full or impacted anal sacs, which are small glands near the anus that can become swollen or infected, causing pain. Dogs drag their rear on the floor to relieve this pressure. Other causes include allergies, parasites like tapeworms, skin infections, pain in the lower back or hips, and sometimes tumors or other health conditions. If the behavior is frequent or accompanied by symptoms like bleeding, swelling, discolored trails, or a strong odor, a vet visit is recommended to diagnose and treat the underlying cause.