Most of the yellow discharge on underwear is caused by vaginitis, a condition in which bacteria, mycobacteria, trichomonas and other pathogens cause damage to the vagina, resulting in increased discharge and also a change in the color of the discharge, which can lead to the appearance of yellow discharge. If the patient has cervicitis or cervical erosion, this discharge may also occur. Therefore, this condition is mostly caused by inflammatory gynecological diseases. Patients should go to the obstetrics and gynecology department of the local public hospital for laboratory tests of the discharge, colposcopy and internal gynecological examination to clarify the diagnosis of the disease and, according to the test results, choose appropriate medication under the guidance of the doctor.