Painless rash on penis after sex

About 10 weeks ago (8/13/04), I received unprotected oral sex with a high risk partner (a dancer at a bachelor party). About 10 days later I started to experience burning during urination and one swollen lymph node on my thigh. I went and saw a urologist and was told it was mild urethritis and it would clear up on its own. I was not given any medication since my urinalysis looked fine. The symptoms did go away shortly afterwards.
I am married however, and was very concerned about giving my wife something so to be 100% sure I was tested for chlamydia/ghonorrhea the day after I saw the urologist. Both were negative. About 45 days after the encounter, I got tested for herpes as well just for peace of mind. It came back negative also. I assumed all was well.
My wife and I did not have unprotected sex for 30 days (until 9/13/04) after my encounter because she was off her birth control pills. Since then we have been have been engaging in regular sex without a condom since she is back on the pill. Last week however (10/12), one day afer sex I noticed a small red rash on the base of my penis. It was a solid red line in one of the folds of skin near the base that runs parallel to my foreskin scar. It was barely visible unless I stretched the skin or I had an erection. It did not really burn or itch at all. I thought it was jock itch and put tinactin on it and it went away. The next time my wife and I had sex, it came back however it the same place as well as appearing in a few more folds of skin along the length of the shaft. I got very worried that I had given her something and went and saw a family practicioner. He said there were no blisters or sores and that it did not look like an STD, but he did not know what is was. He gave me a prescription for an antifungal and told me to see a dermatologist or urologist if it persisted. I am freaked out though because it only appears after sex. Do you have any idea what this might be?
Once again, the rash appears as a a few solid red lines in the folds of skin on the shaft of my penis. When I stretch out my penis or it is erect, it looks like a few spaced out red lines have been drawn across it. They are not raised and I do not feel a noticeable difference in the skin around it. It always appears in the same region and does not really itch or burn, and it goes away after a few days, only to return after sex. Do you have any idea what it may be, and should I be concerned about having transmitted an STD to my wife? Any help will be greatly appreciated. Thank you.

[Alan Rockoff, MD]

Yes, I think it comes after sex, because it is redness from friction and irritation.  Things that come in geometric patterns (like lines) are usually the result of trauma of some sort, in this case probably friction.  I think you have done more than reasonable due diligence to rule out STD.  For definitive diagnosis, show these lines to a dermatologist.

Best.

Dr. Rockoff

[dayz33]

A related discussion, i have some painless rashes on my penis cap was started.