red mark on shaft of penis

I had unprotected oral sex with a girl, and I then had protected vaginal sex with her.  About 10 days later, I noticed a red mark on the top of the shaft of my penis and an inch away from my pubic region. The next day the mark was a little bit bigger (pea size, maybe a little smaller).  The mark is fairly bright and becomes bright red and sheds skin when I shower.  There is no fluid or discharge.  There is no burning or itching or any feeling at all with it, but it is visible.   I believe the mark was slightly raised from the surrounding skin, but now (5 days later) is it not raised at all, but still pretty red and shed skin in the shower today.  I stretched the skin and it is not raised at all, but looks red and irritated.
Does this describe any type of std?  I plan on seeing a doctor, but would like to know what your best guess is from the description?

[Alan Rockoff, MD]

I think you're describing irritation, not an STD.  I think your best bet is to leave the spot alone in order not to irritate it and to show it to the doctor when you go.  If you can, take a photo of what it looks like now, to show the doctor.

Rake care.

Dr. Rockoff

[redmark]

Also, if it is a possible std, would it definitely show up in a blood test next week, or would I have to wait months for a definitive answer?

[Alan Rockoff, MD]

No (not all STD have relevant blood tests, especially early on), but examination should suffice.

Dr. Rockoff