Why is it black around the vulva?

Around the female vulva is black, most belong to the normal physiological phenomenon. Vulva is black, therefore, is in the body after puberty estrogen levels began to rise, make the vulva mucosa showed the phenomenon of coloring, girls before puberty, vulva skin color and the surrounding skin color is the same, only after entering puberty, vulva skin color will show the phenomenon of coloring, that is, the color of the local will be more black than the color of the surrounding skin, this is a normal phenomenon, do not need special treatment. Normal women to ensure that the vulva clean, to prevent bacterial infection, menstrual period frequently in sanitary napkins, frequently in underwear. Girls after pregnancy around the vulva black phenomenon, and even more obvious.