Secretion of black mucus is related to gynecological diseases, such as cervicitis, endometritis, cervical cancer, gynecological malignancies and lesions, etc. Black mucus of secretion can occur. It may also be related to unclean menstruation, because the black and brown discharge is produced by the oxidation of hemoglobin mixed with vaginal secretions after a small amount of bleeding from the uterine cavity. Don’t worry, it will be gone in 1-2 days. Then there are endocrine-related diseases that may cause black viscous vaginal discharge, such as bleeding related to birth control pills, dysfunctional uterine bleeding, intermenstrual bleeding, postmenopausal uterine bleeding, etc. Normal vaginal discharge is milky white and odorless. If the discharge turns yellow, green or black, it is related to gynecological disorders and should be treated promptly at a hospital under the guidance of a doctor. Vaginal discharge is a white, odorless discharge that fluctuates periodically due to the menstrual cycle.