Cat has oozing, bloody sores at the base of his tail. As one spot heals, another one appears next to it and is traveling around the tail. Hair grows back after the small sores heal.
If Jagger goes outdoors he may be developing abscesses at the base of his tail that are rupturing and healing - abscesses most often form after a cat bite. He may also have a dermatological condition like allergies, fleas, or 'stud tail' that is causing bacterial infections at the base of his tail. I would recommend making an appointment with your veterinarian to have these sores examined. He may need antibiotics.