To wash your hands, or not to!

So your saying 2 guy in the desert could live several more weeks by pissing in each others mouth ?

The problem with doing that is that you remove bad stuff from your body when you urinate. This is why, for example, you have to urinate more often when drinking caffinated soda than when you drink water: your body is trying to get rid of the caffine. If you have a machine to take that stuff out, then it'd work fine, but otherwise, you're just making the stuff build up in your body.