I am a fair-skinned, blond 21 year-old female. When I was about 12 I discovered a large, darker-colored splotch on my stomach and hip (it looks like a birthmark, but my mother said I wasn't born with it.) It has grown with me through the years. It is just as sensitive to the touch as the rest of my skin and there is no itching or anything unusual except the color. (I have had two children and although I did get stretch marks on the rest of my stomach and other hip, I didn't get a single one in the darker skin.) A couple of years ago, I noticed a smaller splotch of the same nature on my leg. I also have a dime-sized white spot on the underside of my wrist and on a couple of my nuckles that become accentuated in the summer.
Could this be anything serious, or is it only cosmetic? Is there something I could put on it to even out my skin color in those areas for appearance's sake?