hi, thank you for your query. Dark skin in the inner thigh regions is due to many reasons- *OverweightExcessive or extra weight *Acanthosis nigricans-A brown to black, poorly defined, velvety hyperpigmentation of the skin. it is usually found in body folds, such as the posterior and lateral folds of the neck, the axilla, groin, umbilicus, forehead, and other areas. *Insulin resistance-Condition in which normal amounts of insulin are inadequate to produce a normal insulin response from fat, muscle and liver cells. ... *Chafing-The process caused by constant rubbing against of the thighs leads to discolouration. *since you didnt mention your sex,if you are a female then PCOS is a major cause. Treatment- *the regions should be comfortably clothed.It s important that the areas are allowed to breathe in comfort, so avoid wearing tights/ fitting underwear while going off to sleep. *Avoid exposure to synthetic or nylon materials rather go for cotton and natural fibers *It is important to keep the areas thoroughly cleansed, but avoid exposing the folds of inner thighs and underarms to hard scrubbing agents. *In order to cleanse it of dirt and other impurities, a cream based scrub such as apricot scrub can be used. *The areas should be soothingly moisturized following the process of cleansing. *Make it a point to have the regions patted dry with a cotton towel. Moisture should not be allowed to breed. *Weekly regimen of exfoliation is one of the effective tips on day to day care. Soothing lotion or a moisturizing cream can also be applied as part of daily care. *Gel extracted from aloe can also be applied *Drink plenty of water and fruit juices to keep your system thoroughly hydrated. *Potatoes are an excellent bleaching agent. Chill slices of potatoes and place them on the dark skin of the thighs. Leave for some time and wash the area with warm water. you can use the above tips and results can be seen in a month. thank you, wishing you good health