The human body is as leaky as a sieve. It sweats, spits, pisses, poops, bleeds, and sprays. But all those flowing fluids are essential for the healthy functioning of the body. Without saliva we can’t swallow or digest our food; without clotting blood our wounds won’t heal; without vaginal fluid and sperm, we couldn’t reproduce. Nowadays we quickly find pus, sweat and urine dirty and unhygienic, but that hasn't always been the case. How did that change?