If you’ve ever pulled a pair of underwear out of the laundry only to notice strange light patches or discoloration in the fabric, you’re not alone. Many women have experienced this odd phenomenon, but few realize what’s actually causing it.

While it’s easy to assume your washing machine or detergent is to blame, the real culprit is something completely natural—your own body.

According to a female obstetrician-gynecologist who goes by “The Vag Doc” on TikTok, this so-called “bleaching” effect is caused by the acidity of vaginal discharge.

The Science Behind the “Bleaching” Effect

In a now-viral video, The Vag Doc explained that the vagina maintains a delicate balance of bacteria, primarily lactobacilli, which help keep the area healthy. This bacteria creates an acidic environment that prevents infections and maintains overall vaginal health.

“When your vagina is working as it should, it has a specific pH balance that includes lactobacilli and other bacteria,” she explained. “This acidity is essentially what helps keep your vaginal microbiome in check.”

But here’s where it gets interesting: that same acidity is also responsible for lightening or “bleaching” the fabric of your underwear over time.

“If your discharge is more acidic, it can actually strip the dye from your underwear, leaving behind lighter patches,” she said.

Is It a Sign of a Problem?

The good news? This bleaching effect is completely normal and doesn’t mean anything is wrong. In fact, it’s often a sign that your vaginal pH is exactly where it should be.

“A normal, healthy vagina can sometimes cause discoloration in underwear, so there’s no need to panic,” she assured viewers. “It’s just science at work.”

What If Your Underwear Doesn’t Change Color?

Some women in the comments had concerns that their underwear had never shown signs of bleaching. Was that a problem?

“Not necessarily,” The Vag Doc explained. “Some people just have less acidic discharge than others, and that’s as well normal.”

Another viewer asked whether different fabrics or dyes could affect how much bleaching occurs. The answer? Absolutely. “The type of fabric, its color, and the dye used in the material can all influence whether or not you notice bleaching,” she confirmed.

When to Be Concerned

While some vaginal discharge is completely natural, certain changes can signal a problem. The Cleveland Clinic advises women to seek medical attention if they notice unusual changes in their discharge—such as a strong odor, a different color, or a change in texture—as these could indicate an infection or other health issue.

But as for that unexpected bleaching in your underwear? That’s just your body doing what it was designed to do.