What Causes Red Itchy Rash On Inner Thighs?

Yesterday I noticed a red itchy rash developing on both my inner thighs. After looking up a few things I put hydrocortisone cream on it before bed. The rash was still there the next morning. There are no blisters or pusd but is like huge. Solid light red rash. Im going to try anti fungal cream nect. How long does thing like heat razh ,ring worm, or allergic reaction supposed to last,??? Im freaking out