36. Ancient Romans Routinely Used Urine in Dental Hygiene
Urine’s active ingredient is ammonia, which the body secretes in the form of urea. Today, we use ammonia in many things, from explosives to cleaning products to agricultural fertilizers. Not only will ammonia remove stubborn stains from your bathtub and oven, it will also leave your dishes and glasses twinkling.
In the modern era, we usually extract ammonia with chemical process that do not rely on pee. The ancient Romans did not have access to modern science, but they still understood the benefits of ammonia. So they got it from the most readily available source back then: piss.