I have read that oral sex is a low risk over and over again. But im confused why. I know that hiv can be transmitted through any membrane such as the urethra. But isnt the lineing of your mouth also a membrane? Ive also heard that the trace amounts of digestive acid in saliva instantly kills the virus. Is that true? Thanks so much.

Hello,

You are correct: oral sex is indeed considered to be only a low-risk activity vis-à-vis HIV transmission. There are a variety of reasons for this, including that not all mucous membranes are the same. Some, like that in the mouth, are much more durable than the mucous membrane of, say, the urethra. Also, saliva does contain substances that have anti-HIV properties. Third, the chance of trauma from the amorous activities involving various "poles in holes" is less in the oral cavity than, say, in the anal canal. So, these among other factors contribute to oral sex's "low" risk rating for HIV transmission.

Dr. Bob