Hi First you need to find out what is causing this pigmentation. There are many causes like frictional hyperpigmentation due to frequent rubbing or due to excessive use of otc skin lightening creams or even due to underlying hormonal changes. Please contact a dermatologist who offers skin testing and then plan for further treatment. Use of sunscreen as well as a healthy diet with help with skin lightening. Oral anti oxidant tablets as well as vitamin creams can also help. As a last resort you can also consider Q yag Laser treatment