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 or send photos with detailed history using online consult option for proper treatment.,

Greetings. There can be few medical conditions associated with such presentation and should be ruled out by meeting a Dermatologist. The information provided is limited. A thorough history and clinical examination will be helpful. A photograph will add in obtaining better recommendations.