What Is The Remedy For Itchy Rash Around Anus?

i have itchy rash around my anus , maybe 3"x3". it itches , burns , hurts to wipe, or wash with water.its been there for 4 or five days. first day i had baby powder on it but it still seemed to stay moist. second day cortizone cream. and the last two days just been trying to let it airout.but seems to always be moist