If you have black mucus coming out of your vagina, it depends on what period of time you have the discharge. If you have your period coming soon, you may have a black discharge because of a small amount of vaginal bleeding due to coldness in the uterus. There may also be a small amount of brownish discharge towards the end of your period, which may be due to vaginitis or other inflammatory problems. In the ovulation period there may be dark brown discharge, may also be ovulation bleeding will have, pay attention to hygiene can, do not worry too much. There are symptoms of uterine cold can eat traditional Chinese medicine, vaginitis need to check the leukorrhea, and then symptomatic treatment, ovulation bleeding need to enhance the immune system, the serious situation may be the need to use hormone regulation.