Despite its many advantages, perhaps the internet’s greatest gift is access to limitless shared knowledge. You can find answers to almost anything—mysteries that once stumped us for decades can now be solved in moments with a quick search.

For example, many women have wondered why their underwear sometimes appears bleached. While some blame washing machines, the real reason lies in biology.

These light patches are typically caused by the vagina’s natural pH levels. A healthy vagina is mildly acidic, with a pH between 3.8 and 4.5. This acidity can actually cause fabric to discolor over time. Far from being a sign of poor hygiene, it’s often an indication of a healthy, self-regulating system.

Dr. Vanessa MacKay of the Royal College of Obstetricians and Gynaecologists confirms that the vagina cleans itself with natural secretions and beneficial bacteria. According to the NIH, disrupting this balance can lead to infections.

So, those “bleach stains”? They’re normal. Spread the word—because the more we know, the healthier and less self-conscious we can all be.