Peeing in the shower is one of those things a lot of people have done at some point but may be reluctant to admit. It makes such perfect sense on a practical level, though! You also may have heard that urine is sterile, so you can pee on yourself with abandon and still technically be clean. Here, experts weigh in on this pressing question. Your pee is mostly water, according to the Mayo Clinic. However, it can contain a bunch of other stuff, too, Stephanie Kielb, M.