Bleach-like stains on underwear are usually harmless and caused by the natural acidity of vaginal discharge. As the article explains, “due to its slightly acidic pH, normal discharge can gradually bleach fabric,” showing that the body’s protective system is working properly.

Normal discharge is clear to milky white, mild in scent, and changes during the menstrual cycle. These variations can leave marks without signaling a problem.

However, changes in discharge may point to health issues. A “fishy smell may point to bacterial vaginosis,” while itching, burning, or irritation often indicate yeast infections or pH imbalances. Discharge that is green, gray, yellow, or has a thick cottage cheese–like texture can also signal infection.

Other symptoms that require attention include pain during urination, discomfort during sex, pelvic pain, or watery discharge suggesting bacterial overgrowth. Bleeding between periods or blood-tinged discharge could mean hormonal or cervical issues and should be checked promptly.

Most stains are harmless, but “symptoms that persist or worsen should not be ignored.” Good hygiene, breathable underwear, and regular checkups help maintain balance, while early medical care prevents complications like chronic discomfort or fertility concerns.