Hi!
The itch could be due to sweat dermatitis. It could also be a fungal infection like tinea cruris. Keep the area dry, wear loose fitting clothes, and change undergarments at least twice a day. Many treatment options are there like Clotrimazole 1%, Miconazole nitrate 2%, Tolnaftate 1%, ketoconazole, terfibnafine and Butenafine hydrochloride 1%. Many OTC products containing these salts are available, your pharmacist can help. Try a combination of two and apply until the round marks you see disappear. Continue application for 2 weeks after the marks disappear. The cause for persistence is that the treatment is often left in between. After the itch and dryness goes, you have to continue applying for at least another 2 weeks for the infection to be completely cured from the lower most layer of the skin. Wash your hands well and dry them properly both before and after the application. Meanwhile test for blood sugar level to see if it is high for diabetes too can prevent resolution of fungal infection. Take any anti-allergic tablet or antihistamine to overcome itching. Since a confirmed diagnosis is not possible on net, consult your doctor once. Take care!