I recently had unprotected sex and a darker patched area, where the other person (female) and I (male) where in contact seems to have formed, with no pain or itching. Sex took place 4 days ago but have only noticed now due to shaving and uncovering said area. Please note, rashes did tend to occur with past partners in long term relationships as well due to sensitive skin. However since this occasion was specifically unprotected, I am somewhat concerned. Could this possibly be a symptom of and STD? Thank you!