Romans used urine as mouthwash

Romans actually used urine as a surprising dental whitener! Its ammonia content helped clean teeth and banish stains. This clever use of a readily available resource highlights their early understanding of hygiene and even led to a dedicated urine-collecting industry. It’s a bizarre but fascinating glimpse into ancient Roman life.

Ancient Romans used human and animal urine as a mouthwash and tooth whitener because the ammonia served as a powerful natural cleaning agent. While repulsive by modern standards, the practice was so widespread that the Roman government actually taxed the collection of liquid waste.

The Liquid Gold of the Roman Empire

• Chemical Property: Ammonia acts as a mild bleach and effective degreaser.
• Economic Impact: Emperor Vespasian famously taxed the collection of urine from public urinals.
• Geographic Preference: Portuguese urine was considered the premium high-potency choice for dental care.
• Cultural Record: The poet Catullus mocked a rival for having teeth that were too white, attributing it to heavy urine usage.

Why It Matters

This practice reveals a sophisticated, if visceral, understanding of chemistry long before the formalisation of the periodic table, proving that Roman vanity was powerful enough to override the gag reflex.

The Chemistry of a Pristine Smile

The Roman obsession with pearly whites was not just a matter of aesthetics; it was a display of status. They achieved this using what they called lotium. When urine is left to sit, it decomposes and produces ammonia. This nitrogen-hydrogen compound is a weak base that excels at removing organic stains and neutralising acids that cause tooth decay.

In contrast to modern abrasive toothpastes that use silicas to scrub the surface, the Roman method relied on chemical bleaching. It was effective enough that the practice persisted in various forms until the 18th century, appearing in the medical texts of the era as a legitimate treatment for gum disease.

The Business of Waste

Urine was such a valuable commodity that it supported an entire industry. Fullones, or Roman laundry workers, used massive vats of aged urine to bleach linen and remove tough stains from togas.

Because the demand exceeded what a single household could produce, public basins were placed on street corners for passersby to use. This led to one of history's most famous fiscal anecdotes. When Titus, the son of Emperor Vespasian, complained about the disgusting nature of the urine tax, his father held a gold coin to his nose and uttered the phrase: Pecunia non olet. Money does not smell.

Evidence from the Archives

We know of this practice not through archaeological residue, but through the sharp tongues of Roman writers. The poet Catullus, writing in the 1st century BC, provides the most damning evidence. In his Poem 39, he mocks a man named Egnatius for his constant, beaming smile.

Catullus notes that Egnatius is from Celtiberia, a region where, according to the poet, men rub their teeth and red gums with what they have excreted. He concludes that the whiter a man’s teeth are, the more urine he must have consumed.

Modern Comparisons

While the thought of using urine today is unthinkable, the chemical logic remains sound.

• Modern Bleach: Most household cleaners and some hair dyes still use ammonia as a primary active ingredient.
• Teeth Whitening: Modern whitening strips often use hydrogen peroxide, which, like ammonia, works through oxidation to break down stains.
• Sustainable Farming: Contemporary researchers at the University of Michigan have explored using diverted human urine as a sterile, nutrient-rich fertiliser, echoing the Roman view of waste as a resource.

Did they use it straight from the source?

No, the urine was typically allowed to sit and age. The process of urea breaking down into ammonia requires time and exposure to air, which increases the liquid's cleansing potency.

Did they use any other ingredients?

Wealthier Romans sometimes mixed the urine with crushed eggshells or pumice to create a primitive toothpaste paste, combining chemical bleaching with physical abrasion.

When did the practice stop?

Urine remained a component in some European mouthwashes until the early 1700s. It was eventually replaced by more palatable chemical alternatives as the field of dentistry became a formalised profession.

Key Takeaways

• Functional Science: The ammonia in aged urine served as a natural whitener and disinfectant.
• Industrial Waste: Urine was an essential industrial chemical for Roman laundries and tanneries.
• Status Symbols: White teeth were highly prized, leading to the use of premium imported urine from Spain.
• Taxable Income: The trade was so lucrative it was taxed by emperors to fund the Roman state.

If the Romans taught us anything, it is that beauty has always required a certain level of sacrifice—though perhaps none so pungent as this.