Black blood on the first day of menstruation is a normal physiological phenomenon, because on the first day of menstruation, the amount of menstrual flow is relatively small, and the blood stays in the uterus for a long time and can’t be discharged in time, which can easily cause the blood to turn black. If the menstrual blood stays in the vagina for a long time, it is easy to cause the darkening of menstrual blood due to the effect of the acidity and alkalinity in the vagina, which is a normal physiological phenomenon. Black menstrual blood accompanied by abdominal pain and vulvar itching may be caused by gynecological inflammation, such as vaginitis, cervicitis, endometritis. These diseases can easily cause dark menstrual blood. It is best to wait until the menstrual period is clean to carry out vaginal secretion examination and cervical examination. If the uterine cold will also appear these symptoms, in the menstrual period need to pay attention to abdominal warmth, it is recommended to drink brown sugar water, you can use a hot water bag to warm the abdomen can be relieved, if necessary, take motherwort and other blood-activating drugs.