I would recommend that you see your primary care doctor
to have this evaluated. If necessary, he or she may refer you to a skin specialist (known as a dermatologist
) who may also be necessary.
What you describe is a very unique and unusual condition. It is not common that skin tags change color. As such, there is no easy answer to your question of what causes them to become white. Because of this, discussing this with your doctor may be helpful.
Part of the problem might be describing exactly what the skin tags are. There are actually many different skin conditions that can cause extra skin. For example, acanthosis is a skin patch of dark skin that often reflects someone at risk for diabetes. These can lighten when weight is lost. Seborrheic keratosis are "tags" that occur often as people age. These occasionally change color, but rarely all at once and all to the same white color.
Actual whitening of the skin can commonly occur. This is caused by a process where the skin pigmentation cells (known as melanocytes) are damaged. Commonly this is referred to as vitiligo. That being said, this affects normal skin and not tags.
Talk to your doctor. There is no easy answer to your question.