Ancient Romans Used Urine as Mouthwash

In the bustling cities of the Roman Empire, a valuable and pungent resource was collected in public amphorae placed on street corners. This liquid, human urine, was a key component in both hygiene and industry. The science behind its usefulness lies in its chemical transformation; when left to ferment in the open air, the urea in urine decays and turns into ammonia. This potent compound is a natural detergent and bleaching agent, making it highly effective for cutting through grease and grime on clothing. Laundry workers, known as *fullones*, would stomp on clothes soaked in a mixture of urine and water to get the famously bright white togas of the elite truly clean.

This same principle was applied to oral hygiene. Believing that the ammonia could disinfect their mouths and whiten their teeth, some Romans used aged urine as a key ingredient in their mouthwash. The practice was so common and the trade so lucrative that the government saw an opportunity. In the 1st century AD, Emperor Vespasian levied a tax on the collection and sale of urine from public latrines. When his son expressed disgust at the source of the revenue, Vespasian famously held up a gold coin and declared, "Pecunia non olet" — "Money does not stink," a phrase that has survived to this day.