There are more reasons for yellow underwear, which may be caused by urine or fecal residue, or gynecological inflammation such as bacterial vaginosis, vulvovaginal pseudomyxoma, trichomonas vaginitis, and so on. 1. Urine residue: yellowing of underwear may be caused by urine not being wiped off in time and remaining on the underwear, making it yellow. 2. Fecal residue: If you don’t wipe the feces clean after defecation, the residual feces in the anus may make the panties yellow. 3. Bacterial vaginosis: If bacterial vaginosis is present, there may be yellow marks on the panties as the discharge may appear yellow or yellowish green. 4. Vulvovaginal Pseudomonal Yeast Disease: In vulvovaginal pseudomonal yeast disease, there is a possibility that the panties may be stained by the secretions and the panties may appear yellow or white. 5. Trichomonas vaginitis: if the patient is infected with trichomonas, the vaginal secretion produced by trichomonas vaginitis drips down on the panties, which may make the panties appear yellow. The yellowing of the underwear alone can not accurately determine the cause, but also need to be combined with the characteristics of the medical history, other test results in order to make an accurate judgment, it is recommended that the cause of the disease under the guidance of the doctor to clarify the cause of the disease, targeted treatment.