Pain in the lower part of the body during menstruation, also known as perineal swelling and pain, may be caused by symptoms of pressure and irritation due to pelvic congestion during menstruation, or it may be caused by endometriosis. During menstruation, the pressure and irritation caused by pelvic and genital congestion leads to perineal swelling and pain, and the symptoms usually decrease or disappear at the end of menstruation. Endometriosis can also present with dysmenorrhea, where the pain radiates to the perineum, causing swelling and pain in the perineum. If endometriosis is diagnosed, non-steroidal anti-inflammatory drugs (NSAIDs), progesterone and other medications can be given under the direction of a doctor depending on the specific condition. In addition, gynecological inflammation can also cause perineal pain, which needs to be treated according to the specific condition. In the clinic, if the pain in the perineum is obvious during menstruation, it is recommended to go to a regular hospital to complete the relevant examinations to confirm the diagnosis, and not to blindly self-medication, so as to avoid delaying the condition.