Recetly I used aother man's semen for lube to masurbte myself. I now realize there is danger in doing this, as it can come into contact with the mucus membranes of the urethra. I was wondering just how dangerous this is considered to be?

It's difficult to say how "dangerous" it is to use another person's semen for lubrication of your penis; frankly, there is no need for alarm. What we know about HIV transmission during sexual contact is that it is limited to vaginal, anal, and, less frequently, oral sex. This means that transmission of HIV through masturbation with another person's fluids would be an unlikely occurrence. HIV's fragility when exposed to the environment can be one explanation for the low-risk nature of this activity.

In some of my responses about mutual masturbation, I recommend that people do not use another person's fluids (semen, vaginal secretions, or fluids containing blood) for masturbation (saliva is not included in this list because it is not implicated in transmission). It is generally wise to avoid mucous membrane contact with potentially infected fluids because transmission of HIV could happen, even if it is unlikely. Use water or oil-based lubricants for masturbation; some are available in pocket sized packets or tubes in case you're out on the town. If no lube is available, use spit (saliva) instead of the semen of a person whose status is unknown or positive.

You may be at greater risk for other sexually transmitted infections through the activity you describe. Gonorrhea, chlamydia, hepatitis B, and syphilis are ones to be on the lookout for, because they can be transmitted through contact with infected semen.

RMK