Oral to Genital...how common?

Last night I received oral sex from my girlfriend. I didn't notice until after it was over that she has a "cold sore" starting on her bottom lip. She didn't notice it either until I pointed it out. I work in healthcare, so I am somewhat familiar with the risks but need an MD's opinion. What is my chance of contracting HSV from the experience? It was about a 15-20 minute thing. I have recently been tested and have a clean bill of health from HSV 1/HSV 2 and every other STD. She has a RX for Valtrex because of the cold sore situation. Is there any research to determine if you can use Valtrex for PEP as in an HIV infection? How soon if so should I have symptoms? Is there anything I can do but wait and see? I know it sounds extreme, but I scrubbed with Ethyl Alcohol 71% after I noticed the cold sore coming on her lip in hopes that if it were on my skin that it would kill the virus.

[Edward W Hook, MD]

You have posted on the wrong site.   Questions about STDs (herpes) belong on the STD forum site.  I will do my best to answer your questions with this reply but, if you have additional questions or follow-up they must be on the STD site.  Sorry

There is not much data to answer the question you ask.  We know that most exposures to herpes do not lead to transmission of infection.  We also know that there is more virus present when a cold sore is present than with asymptomatic shedding.  Bottom line, you are exposed and may have to wait it out.  Several other facts however.  For one thing , even though you may not have cold sores, you may have antibodies to HSV-1; this is actually quite common with about 60% of adults having antibody.  If you do, you will have a degree of protection from your existing immune response.  If you don't then it is a matter of chance.  The incubation time of HSV lesions is typically 2-7 days; if no lesion past 10 days you almost certainly did not get infection from the exposure you describe.  

The effect/benefit of scrubbing is, as you might imagine, unknown.

As far as HSV PEP is concerned, no studies.  Given the differences in biology (HIV infects lympocytes and related cells, HSV infects nerve cells, starting at the site of inoculation) PEP might theoretically be less effective for HSV than HIV.  If it were to be effective the sooner started the better.  For HIV, the recommendations are within 48 hours.  If anything, the interval to be effective could be shorter for HSV.  Sorry I don't have more information.  Good luck.  EWH