How often should you change your sanitary napkin during menstruation, preferably in less than two hours. If the menstrual flow is heavy, the time may be shorter. Sanitary napkins are not breathable , and if you do not change sanitary napkins diligently during menstruation, your perineum will be stimulated by humidity for a long time, and you may experience itching and skin redness of the vulva. If you do not change sanitary napkins for a long time, bacteria will easily grow in the blood, and the cervical opening is dilated during menstruation, and bacteria may travel up the infection, causing endometritis, etc. Pay attention to maintaining perineal hygiene during menstruation, you can wash your perineal area every night before going to bed. You can take a shower during menstruation, not a sitz bath, to avoid infection. Avoid cold and strain during menstruation, and do not eat spicy and stimulating food.