The mystery behind bleach-like spots on underwear has been solved. It turns
out that the natural pH levels of the vagina, which range from 3.8-4.5, can
cause a “bleaching” effect on fabric. This is completely normal and not a sign
of poor hygiene or a washing machine issue. Many people have shared that this
is a common and healthy occurrence, with some even tweeting about it.
So, lighter patches on underwear are a natural result of the vagina’s acidity