A: Well, for the underarm area, one thing that contributes to the skin’s darkness is the shadow of the hair roots in that area so your hair removal method could influence that. Having said that, to make any changes to your skin in these two areas a consultation with a dermatologist would be much more valid.
As far as sexual health concerns, the darker color of a women’s genital area and the around their nipples shows that she has matured sexually and has fertility capacity. The skin of these areas especially the Areolas (around the nipple) could get darker during pregnancy. This is because of a higher level of melatonin (the natural pigment that your body produces that gives color to your hair, skin and eyes) . In most women it goes back to normal after they stop the breastfeeding. Therefore, from sexual health perspective, it is not only normal and doesn’t need curing but also something to be proud of!
These days I get asked this question more than before and I wonder if it is because of the observations women (or their partners) make in the professional porn movies where the actresses usually have been through plastic surgery or chemical procedures (e.g. bleaching) to change the form of their genitalia or lighten their skin (to look more adolescent-like).