Behavioral Ecology Blog

Basically- don’t do it too soon after unprotected sex.

A study in Uganda has come up with a surprising finding about sex and H.I.V. Washing the penis minutes (which is apparently very common in Africa) after sex increased the risk of acquiring H.I.V. in uncircumcised men.

So says a NYT story that is based on research presented by Dr. Fredrick E. Makumbi at the International AIDS Society Conference in Sydney…

Although the authors don’t give a precise reason why, I think that it is intuitive…Think about the epidermis, its job it to maintain impervious to environmental bacteria, viruses, etc. Now think about the friction the occurs during sex (OK pervert, don’t think too hard), the epidermis is stretched, and microscopic perforations are created. Each of these tears is a potential portal of entry for pathogens. Washing does 2 things.

1. I bet that washing with water (and more friction) prolongs the time that these micro-lacerations remain open.
2. Porosity- the skin becomes more porous with the addition of water, such that thinly stretched (but not quite broken) skin becomes permeable to viruses..

As the authors report, delaying washing >10 minutes eliminates the additional risk of washing.. I bet that 10 minutes is enough time for the majority of these micro-lacerations to be infiltrated by clotting materials…

So although washing is usually recommended, guys, enjoy the afterglow a few more minutes and reduce your risk..