QUESTION
In the last few days, I have noticed a light yellow stain on my underwear in the vicinity of the head of penis. Could this be a symptom of an STD? If so, what could that be? I don't feel any other symptoms whatsoever. If I get infected with an STD, what is the chance that my partner would get it if I only have sex with that person once? Thank you.

ANSWER
If you are sexually active and have had recent oral, anal or vaginal sex, you certainly might have something. A yellow stain on the underwear is a fairly common sign of urethral discharge. You must see a medical provider, which you should do immediately. Ask for a routine STD testing and be sure to mention the symptoms. You can also have an STD with no symptoms, so if you're sexually active, you should be getting routine STD checkups every 3-6 months.

If you do find that you have an STD, get it treated and be sure to let your sex partners know, so that they can get treated and not pass it back to you. To tell your previous and current partner(s) you have an STD, you can use inSPOT.org -- a free, anonymous way of telling previous partners they may have been exposed to an STD.

To get tested for STDs, you can go to the San Francisco City Clinic at 356 7th Street, San Francisco or see your private doctor. City Clinic is a drop-in clinic open from 8:00-4:00, M-W-F, 1:00-6:00, Tuesday, and 1:00-4:00, Thursday. The phone number is 415-487-5500.

To your health,
Dr. K