I am a cis gender male and have a rash high up on my left and right inner thigh. It is right next to my genitals and is in contact with them but has not spread to my testicles or penis. I first noticed the rash about a week ago after i finished a run. The last time I had unprotected sex was about a three weeks ago. The girl I was with had absolutely no symptoms or signs of anything near or around her genitals. The rash itself only itches slightly when it dries out, If I put lotion on it there is no discomfort whatsoever. It seems to have gotten slightly better in the last few days. There is no puss or any other open wound from the rash. The rash is read and circular and slightly raised from the skin. I also spend many hours in a chlorinated pool on Saturdays which dries out my skin quite a lot. I'm thinking that the rash could be a combination of the dry skin and running but obviously its location makes me a little worried. I'm wondering is there an STD that would start on the thigh and then move to the genitals after a week+ of only being on the thigh, in your opinion would you lean towards this being a simple rash from dry skin, chaffing and hot weather or an STD?

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Thank you very much for this information Dr.Hook. As a quick follow up to put me completely at ease. Can you confirm that an STD would not start on the thighs and stay there for a week with direct contact with the genitals without spreading in any way? 

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