Herpes?

Hello there. Two and a half weeks ago I had an unprotected one night stand with a girl who has had multiple unprotected encounters in the past. Approximately two weeks after the encounter I began to develop a bit of a rash.
The shaft of my penis has a few small splotchy, shiny patches. The skin where the splotches are seems to be dryer than the rest of the penis. I

[H. Hunter Handsfield, M.D.]

This sounds most like a fungal (yeast) infection, or perhaps contact dermatitis, ie allergy perhaps to a vaginal hygiene product.  Herpes is always a consideration with inflammatory genital lesions after sex, but this doesn't sound like herpes.  However, the 2-week delay is a bit too long for all these possibilities, and it is possible the rash is coincidental with your sexual encounter.  Non-sex-associated possiblities include contact dermatitis due to, say, residual detergent in your underwear; allergic rash (Probecia??); psoriasis; a dermatitis called lichen planus (common in the genital area--look for a purplish sheen); and others.

You could consider trying an OTC antifungal cream; look for the jock-itch products.  If that plus regular washing doesn't clear it up, see a health care provider, preferably a dermatolgist.

I doubt you have an STD.  Good luck--

HHH, MD