Hi, Dark inner thighs are a common occurrence, with several possible causes. There are many reasons as why inner thighs darken, profuse sweating, razors, and certain lotions and creams are some of the major causes. Being overweight can cause your thighs to rub against each other when you walk, which can cause discoloration and itchy skin called chaffing. To avoid this wear loose-fitting pants and avoid nylon and other synthetic fabrics as they cause more irritation, choose natural fibers when possible. Consult Dermatologist...