Ancient Romans Used Urine as Mouthwash

The value of urine in ancient Rome extended far beyond a simple waste product; it was a sought-after commodity with surprising applications in daily life and industry. The key to its usefulness lay in its chemical composition. When left to decompose, the urea in urine converts into ammonia, a powerful cleansing agent. This natural chemical process made stale urine an effective stain remover and whitener, leading to its use not only in dental hygiene but also for laundering togas and tanning leather. This practice continued for centuries, with urine being a key ingredient in mouthwashes and toothpastes until the 1700s.

The demand for this unlikely resource was so high that it was collected in public vats and sold. Romans believed that the most potent urine came from Portugal, and they were willing to pay a premium for this imported product, which was considered the best for achieving a bright smile. The Roman poet Catullus even satirized a contemporary for his gleaming white teeth, attributing them to the use of Spanish urine. This thriving trade did not go unnoticed by the imperial authorities.

The commerce of urine became so significant that it prompted Emperor Nero to introduce a tax on its collection and sale in the 1st century AD, known as the "vectigal urinae". Although briefly repealed, the tax was later brought back by Emperor Vespasian to help refill the empire's depleted treasury. When Vespasian's son, Titus, expressed his disgust at the tax's origin, the emperor famously held up a gold coin and declared, "Pecunia non olet," which translates to "Money does not stink." This phrase endures to this day, a lasting legacy of a time when urine was a taxable and valuable good.