Another reason for tail rubbing

My gelding rubs his tail to let me know that his sheath needs cleaning (“Investigating Tail Rubbing,” Hands On, EQUUS 469). When he first began to do this, I thought he was itchy at the base of his tail and around the tailbone due to dry skin. I tried baby oil, but he continued to rub. I then discovered his sheath was dirty and bothering him---once I cleaned it, he stopped. Elaine Cohen Staten Island, New York