You read that right. Urine. In the mouth. The Romans were brilliant road builders, fearless engineers, poets with bite—and enthusiastic recyclers. They used what they had, and in a city of a million people, they had plenty of this particular “resource.” So did they really swish with it to clean their teeth? Short answer: sometimes, apparently. Longer answer: it’s complicated, a bit gross, and—oddly—pretty logical once you learn the chemistry and the context.
How Roman “clean” looked
The Roman idea of hygiene wasn’t our idea. Daily life smelled like smoke, sweat, fish sauce, olive oil, and animals. Bathhouses steamed. Streets bustled with carts and dung. Laundry shops—fullonicae—sat around the corner from bakeries and bars. These shops did big business using fermented urine for washing tunics. Workers stomped cloth in vats like grapes. Fresh? No. Effective? Yes.
That detail matters. When you hear “Romans used urine as mouthwash,” it’s tied to the broader fact: urine powered an entire cleaning industry. If it cleaned wool, maybe it cleaned teeth too. For some, that leap felt natural.
Why urine does anything at all
Here’s the science in plain English. Fresh urine is mostly water and urea. Let it sit and bacteria break urea down into ammonia. Ammonia is a strong base. Bases cut grease, lift stains, and kill some germs. That’s why ammonia shows up in modern household cleaners. Stale urine becomes slightly ammoniacal, so it works like a primitive degreaser. On cloth, that’s helpful. On teeth, it could strip plaque and brighten enamel—at a cost.
“Cost” meaning it can burn soft tissue, irritate gums, and rough up enamel if used often. Ancient people weren’t studying pH curves or enamel rods. They noticed outcomes. Whiter? Cleaner? Good enough.
Did they actually rinse with it?
Evidence points to “yes, at least some did,” with a heavy dose of satire and side-eye from Roman poets. Catullus mocked a guy with glow-in-the-dark teeth, hinting he owed that sparkle to Spanish urine. Comedy, not dental guidelines, but jokes usually land because they tap something familiar. Later writers tossed in remedies that sound like a wild apothecary drawer: crushed bones, oyster shells, charcoal, salt, ash, vinegar—and yes, urine—show up in Roman-era hygiene chatter. If you’re curious where writers even mentioned this kind of thing, check the grab-bag of folk cures in Pliny the Elder’s Natural History.
So, “mouthwash” wasn’t a formal product with a mint label; it was a home fix some people reached for. If you already stepped into a vat to wash tunics, you might not flinch at a swish.
What else did Romans use for their teeth?
Not everyone was out there gargling. Many used powders: ground charcoal, burnt animal bone, pumice, and shells. These abrasives scrubbed but could chew up enamel. Chewing sticks showed up. Rinses with salty or vinegary water happened. There’s a thread of trial-and-error running through it all. The goal stayed the same: fresh breath, fewer aches, cleaner teeth. The tools? Whatever seemed to work.
The laundry link you can’t ignore
Fullers—the pros who cleaned cloth—needed urine by the amphora. City urinals collected it. People sold it. The emperor Vespasian even taxed the trade. That’s the “money doesn’t stink” moment you might’ve heard—his way of saying revenue’s revenue, no matter the smell. If you want a straight, tidy explanation of that policy and the famous line, read about Vespasian’s urine tax.
The social picture matters: if your town treats urine as a valuable industrial input, the stigma drops. The shop that brightens your toga might brighten your incisors. Same chemistry. Smaller scale. Different target.
Was it safe?
Not really. Ammonia can disinfect, sure, but it also irritates. Enamel doesn’t grow back. Gums hate caustic stuff. Ancient mouths had different threats—no sugar-saturated diets, but plenty of grit, smoke, and infections. People grabbed remedies that gave quick results and didn’t cost much. “Safe long-term outcomes” wasn’t the yardstick. “Does it help today?” was.
Why Spanish urine keeps popping up
Roman satire loves specifics. Spain stands in as a joke-shortcut for strong urine, likely because of regional industries and reputation. Think of it as an old meme: “the good stuff is imported.” Were Romans importing jugs of Spanish swish just for teeth? Probably not. But they did trade and move everything, including materials for fulling. If a poet wanted to poke at someone’s vanity, “Spanish urine whitening” was ripe material.
Could ammonia whiten teeth?
To a point. It breaks up film and cuts through certain stains. It won’t fix deep discoloration. It won’t rebuild enamel. It might make teeth look brighter briefly, especially against a diet that naturally discolors teeth with smoke and wine. But regular use would be rough on the mouth. A short-term shine, long-term damage—classic ancient remedy trade-off.
The smell problem
Let’s be honest. This is the part everyone thinks about first. If it smelled terrible, how could anyone think, “Let’s rinse”? First, once urea turns into ammonia, the odor shifts—still pungent, but in a sharp, cleaner-like way rather than purely “bathroom.” Second, Romans lived with strong smells all day. Their baseline was different. When your city includes tanning pits, fish sauce factories, and baths where thousands sweat together, your tolerance climbs. Plenty of ancient “cosmetics” had odors we’d reject instantly.
What this myth teaches—even when it isn’t a myth
This story gets told at parties because it’s shocking. It sticks because it’s also a window into how Romans solved problems. They were relentless about reuse. They built systems around waste. They taxed it, shipped it, used it in industries, joked about it, and—at least sometimes—put it in their mouths to chase a whiter smile. That’s the mix: hard practicality, public policy, and a cheeky humor that shows up in their poetry.
Don’t try this at home
You knew this part was coming. We have dentists, floss, fluoride toothpaste, and hygienists with superpowers. Use those. If you want the Roman spirit without the Roman mouth, channel the ingenuity and the recycling ethos, not the recipe.
Quick hits for the curious
Yes, some Romans likely rinsed with urine. Mostly as a folk hack, not a medical standard.
The cleaning power came from ammonia. Fermented urine turns into a basic solution that cuts grime.
Fullers used urine by the barrel. It whitened and degreased wool. Same chemistry, bigger vats.
The empire taxed the stuff. Vespasian’s policy is where “money doesn’t stink” comes from.
Alternative Roman dentifrices existed. Abrasive powders, salt, vinegar—no shortage of rough options.
Modern dental science says hard pass. Enamel and gums lose this fight.
If you want to picture it
Imagine a Pompeian street: ruts from cart wheels, painted shop signs, a bakery door open to the heat, a fullonica next door with floor vats sunk like bathtubs. Someone hefts a chamber pot, tips it into a jar, and a runner hauls it to the laundry. Inside, workers step and stomp the day’s tunics, laughing, complaining, getting the job done. Later, a witty poet raises a cup at dinner and roasts a friend for his brilliant smile—“Too brilliant,” he smirks—hinting at the secret ingredient. People chuckle. The joke lands because everybody knows the scent of clean clothes in this town.
The bottom line
“Did the Romans use urine as mouthwash?” Enough did to get noticed. It wasn’t universal. It wasn’t glamorous. It fit their world: clever, thrifty, and unbothered by things that make us squeamish. The surprise fades once you see the pattern. Romans used everything. Even this.
