There are many reasons why your skin would turn dark. Sun tan, overweight, pigmentation disorders like acanthosis or melasma, nutritional deficiency etc are some conditions. Unless someone examines you, we cannot know the cause. Unless we find out the cause it is difficult and pointless to treat. Please call me and visit my clinic for proper treatment. The best treatment for dark circles is chemical peel. Peels can also be done for the whole face.