I was wondering about a strange rash that appeared on my forearm and upper arm it was in a symmetrical rash and reoccured in the same place and in the same shape 4 or 5 times over the course of 6 or 7 months. it was a bit itchy and then it would just go away. The first occurance was about 2 months or so after I had unprotected sex but then it came back several times after that and it has not resurfaced in about a year or so. could it have been a sign of an std?