Pain relievers are really useless.
Ten percent of women have pain so severe that their daily routine is disrupted for one to three days a month. Dysmenorrhea is caused by the release of prostaglandin from the cells that line the uterus. The release of prostaglandin at the time of menstruation causes the uterine muscle to contract. During strong contractions, the blood supply to the uterine muscle is temporarily cut off. This deprives the tissue of oxygen and causes pain.