What Does A Red Rash On The Hip Indicate?

Hello. I had a red, non-itchy, non-painful circular rash on groin/hip area. Treated internally with goldenseal anti-biotic herb, white willow bark anti-inflammatory and externally with charcoal poultice and redness went away after a couple of days but came back 2 days later as circular, raised line but not bumpy. Could this be contact dermatitis? Washed some underwear in soapy water and wonder if the rinse was complete.