Greetings. Firstly - it is normal for the scrotum to be darker than the surrounding skin so dont worry. Inner thigh can be dark due to many reasons - commonly - 1. due to constant friction between thighs/inner clothing - this is more in people who are over weight and obese 2. could be an on going bacterial infection like erythrasma 3. could be ongoing fungal infection or be residual pigmentation after the fungal infection resolves. 4. It may be a combination of the above three For treatment - firstly see a qualified dermatologist. If there is no active infection - mild skin lightening creams can be tried. Hope this helps. Warm regards