In women who are past menopause, a common cause of painful sexual act is having too little estrogen. In women who are breastfeeding, a common cause is dryness of the vagina. Women who are getting radiation therapy for cancer in the pelvic area may have pain during sex because the walls of the vagina have atrophied (wasted away) and are more sensitive to injury. Dryness in the vagina can also be a cause of painful sexual act for women with Sjögren's syndrome, which attacks the glands that create saliva and tears.