Why Ancient Romans Used Urine as Mouthwash: Hygiene History
By Trivia Daily, History Desk — Published July 31, 2026
Table of Contents
- Key Takeaways
- How Ancient Romans Used Urine for Dental Care
- The Economics and Politics of Roman Urine
- What Roman Writers Said About the Practice
- Comparing Ancient Hygiene Practices Across Civilizations
- When Did People Stop Using Urine for Hygiene?
- Frequently Asked Questions
The ancient Romans used urine as mouthwash, a practice that sounds utterly revolting to modern sensibilities but made perfect sense in their world. This wasn’t a fringe habit practiced by a few eccentrics—it was a widespread custom throughout the Roman Empire, endorsed by physicians and embraced by people seeking whiter, cleaner teeth. The reason? Urine contains ammonia, a powerful cleaning agent that effectively breaks down stains and kills bacteria. Before the era of minty toothpaste tubes and antiseptic rinses, Romans turned to one of the most readily available substances in their civilization for oral hygiene.
This historical practice reveals how past societies solved everyday problems with the resources at hand. The Romans weren’t being crude or ignorant; they were being practical and, in their own way, scientifically minded.
Key Takeaways
- Romans used urine as mouthwash because it contains ammonia, which whitens teeth and kills bacteria effectively.
- Imported urine from Portugal was especially prized and even taxed by Emperor Vespasian in the first century CE.
- The practice was so common that public urine collection vessels lined Roman streets for various industrial and personal uses.
- Roman physicians recommended urine for oral hygiene, and the poet Catullus mocked Spaniards for brushing their teeth with it.
- Ammonia remained a key ingredient in cleaning products until modern chemistry developed synthetic alternatives in the 20th century.
- This ancient custom demonstrates how civilizations adapted available materials to meet hygiene needs before industrial manufacturing.
How Ancient Romans Used Urine for Dental Care
The chemical logic behind this ancient practice is surprisingly sound. When urine sits and ages, bacterial action converts urea into ammonia, creating a potent alkaline solution. Ammonia breaks down organic stains, dissolves plaque, and acts as a disinfectant—exactly what you’d want in an oral cleaning agent. Romans would swish aged urine around their mouths, much like modern mouthwash, then rinse with water.
The Roman obsession with white teeth drove demand for effective cleaning methods. Wealthy Romans particularly valued bright smiles as markers of health and social status. Urine-based mouthwash became so popular that it turned into a commodity. Portuguese urine earned a reputation as especially potent, likely due to diet differences that affected its chemical composition, and merchants imported it to Rome in amphorae.
Public collection vessels called “fullonica” stood on street corners throughout Roman cities. While fullers (cloth cleaners) used most of this collected urine for bleaching and cleaning fabrics, individuals could also obtain it for personal hygiene. The practice was integrated into daily life without the squeamishness modern people feel.
The Economics and Politics of Roman Urine
Emperor Vespasian, who ruled from 69 to 79 CE, saw economic opportunity in this widespread practice. He imposed a tax on urine collection from public toilets, turning bodily waste into state revenue. When his son Titus objected to the undignified nature of the tax, Vespasian reportedly held up a gold coin and asked if it smelled bad. The message was clear: money has no odor, regardless of its source. This gave rise to the Latin phrase “Pecunia non olet”—money doesn’t stink.
The urine tax wasn’t just about mouthwash. The Roman economy depended heavily on urine for the massive textile industry. Fullers needed vast quantities to clean, bleach, and soften woolen togas and tunics. The ammonia in aged urine acted as a degreaser and stain remover, making it indispensable for garment production. Personal hygiene use was simply one application among many in a urine-based economy that modern people find difficult to imagine.
What Roman Writers Said About the Practice
Literary references confirm how normalized this practice was in Roman society. The poet Catullus, writing in the first century BCE, mocked a Spanish acquaintance named Egnatius for his perpetual grin, suggesting that the man brushed his teeth with urine so frequently that his bright smile came at the cost of disgusting breath. The insult worked because everyone understood the reference—urine mouthwash was common knowledge.
Roman medical texts treated urine as a legitimate medicinal substance. Physicians recommended it not only for oral hygiene but also for treating wounds, skin conditions, and various ailments. This wasn’t pseudoscience by ancient standards; it was practical medicine based on observed results. The antiseptic properties of ammonia did help prevent infections, even if Romans didn’t understand the underlying chemistry.
Comparing Ancient Hygiene Practices Across Civilizations
| Civilization | Dental Cleaning Method | Active Ingredient |
|---|---|---|
| Ancient Rome | Urine mouthwash | Ammonia from decomposed urea |
| Ancient Egypt | Powdered ashes and crushed eggshells | Abrasive minerals |
| Ancient China | Chewing sticks and salt | Salt as mild antiseptic |
| Medieval Europe | Cloth rubbed with sage or salt | Herbal oils and abrasives |
| Ancient India | Neem twigs (datun) | Natural antibacterial compounds |
Each civilization developed dental care methods based on available materials and cultural knowledge. The Roman approach stands out for its chemical effectiveness, even if the source material makes modern people recoil.
When Did People Stop Using Urine for Hygiene?
The practice didn’t disappear with the fall of Rome. Throughout medieval and early modern Europe, urine remained in use for cleaning, both for fabrics and occasionally for personal hygiene. Ammonia extracted from urine continued as a standard cleaning agent well into the 18th century. Only with the industrial revolution and the development of synthetic chemistry did alternatives become widely available.
The Haber-Bosch process, developed in the early 20th century, allowed for industrial ammonia production from atmospheric nitrogen. This breakthrough eliminated the need to collect and process urine for its ammonia content. Modern toothpaste, first mass-produced in the late 19th century, offered a far more pleasant alternative with added fluoride for cavity prevention—something ancient ammonia couldn’t provide.
Cultural attitudes shifted as germ theory and modern sanitation standards took hold. What once seemed perfectly reasonable became unthinkable. Yet the underlying chemistry that made Roman mouthwash work remains valid; ammonia-based cleaning products still line store shelves, just derived from different sources.
Frequently Asked Questions
Did Roman urine mouthwash actually work for cleaning teeth?
Yes, the ammonia in aged urine effectively removes stains and kills bacteria, making it a functional cleaning agent. While unpleasant by modern standards, it achieved the whitening and disinfecting effects Romans desired.
Was using urine for hygiene unique to ancient Rome?
No, various cultures throughout history used urine for medicinal and cleaning purposes. Romans were notable for the scale and commercialization of the practice, but the basic use of urine as a cleaning agent appeared in many societies before modern chemistry.
Why was Portuguese urine especially valuable in ancient Rome?
Portuguese urine gained a reputation for superior quality, likely due to dietary differences that affected its chemical composition. This created an import market, with Portuguese urine commanding premium prices in Roman markets.
When did people finally stop using urine as mouthwash?
The practice gradually declined through the medieval period and largely disappeared by the 18th century in Europe. Industrial ammonia production in the early 20th century finally eliminated any practical reason to continue the ancient custom.
The next time you squeeze minty paste onto your toothbrush, consider the long, strange journey of oral hygiene. The Romans weren’t crazy—they were working with the best chemistry available in their era. Sometimes the most shocking historical practices turn out to have solid scientific foundations, even if we’re grateful modern alternatives exist.