I have a red area on my front upper thigh. It looks like (maybe) a bite, in the middle, with a large, round, red, irritated area around the center point. A doctor asked about bites, but I don t recall being bitten. We do have woods behind our house and I cut the grass. Doctor prescribed Bactrim several days ago and there has been no improvement. Today I noticed that the red area is starting to turn light purple. Does that mean it is getting better, or worse?