If you've developed dark brown, light brown, or gray patches on your skin, you might have a hyper-pigmentation disorder called melasma. Your dermatologist can help you get a firm diagnosis. Melasma isn't a dangerous condition, but it can be a cosmetic concern for many patients since it causes an uneven skin tone. Take a look at why this condition happens and how to treat it. What Causes it, and Who is at Risk?