Hello, It can be caused by skin infection called Tinea Cruris, visit ER, get physically examined. You may need antifungals (Fluconazole) since you complain of getting such black spots every now & then. You can apply steroid containing creams, like Panderm, Quadriderm in the area affected. Dark circular black spots can be due pigmentation, chafing makes skin thin, itchy & discolored, make sure that your inner thighs do not rub against each other while walking or doing exercises, it may cause a bruise. If you are obese take control of your diet & reduce weight. Take care of your hygiene, avoid use of harsh soaps, wear cotton clothes. Hope I have answered your query. Let me know if I can assist you further. Regards, Dr. Nupur K, General & Family Physician