It is not allowed to have intercourse on the third day of menstruation because most women are not clean on the third day of menstruation and the uterine orifice is open during this period, which can easily cause reflux of menstrual blood and can lead to endometriosis. In addition, it is also easy to cause inflammatory upstream infection, resulting in endometritis, tubal infection, pelvic inflammatory disease and even infertility, but also pelvic inflammatory disease, abdominal pain symptoms, so women during the menstruation is not allowed to have intercourse, can be three days after the clean menstruation and then have intercourse is better. You should not only not have intercourse during your menstruation, but also pay attention to keeping your vulva clean and hygienic and change your sanitary pads regularly to avoid inflammation. You should also avoid eating cold, spicy and stimulating food during your menstruation, and pay attention not to do strenuous exercise.