Pigmentation or darkness of the skin can be because of many causes. Suntan, being overweight that is sedentary lifestyle, some pigmentation disorders like acanthosis nigricans for melasma, nutritional deficiency etc are some conditions. unless I take proper history and examine the affected area, a diagnosis cannot be made. please don't do any home remedies because if they go wrong it can worsen the problem. Please send photos using online consultation for proper examination diagnosis and treatment