The dark brown color of menstrual blood is generally indicative of poor menstrual blood flow and is caused by prolonged stay in the uterine cavity. The main reasons for this symptom include: i. Inflammatory gynecological diseases such as pelvic inflammatory disease and endometritis, which cause the menstrual blood to stagnate in the uterine cavity and appear black in color; ii. Eating too cold food before or during the menstrual period, or staying in a cold environment for a long time, which causes the uterus to contract and the menstrual blood in the uterine cavity cannot be discharged in time; iii. Due to adverse emotional reaction during menstruation, the endocrine function is disturbed and the stagnation of qi and blood causes abnormal discharge of menstrual blood; 4. Repeated abortions or curettage operations cause abnormal menstruation due to adhesion of the uterine cavity or cervix.