If you have sex on your period, you should wash your vulva with warm water immediately after the sex to prevent bacterial infection. Usually, you are not allowed to have sex when you are having your period, because at this time the cervical opening is in an open state, and the menstrual blood is a natural bacterial culture medium, when you have sex, it is easy to bring all kinds of bacteria into the vagina, resulting in a variety of bacterial infections inside the vagina, which can lead to a variety of gynecological inflammation, such as endometritis, adnexitis, pelvic inflammation, and so on. If it is unavoidable to have sex, then it is recommended that the person should use lukewarm water to wash the vulva to avoid any infection. In addition, in general, pay more attention to rest, timely nutrition, as far as possible to reduce the risk of disease. Seek medical attention if you feel unwell.