Ancient Romans Used Urine Mouthwash

While it may seem shocking today, the use of urine for dental hygiene in the ancient world was based on sound, observable science. The key ingredient is ammonia, a compound that forms as the urea in urine decomposes. As a powerful alkaline agent, ammonia is excellent at cutting through grime and lifting stains, which made aged urine a surprisingly effective teeth whitener and disinfectant. This wasn't just a folk remedy; it was a widely accepted practice for achieving the bright white smile that was highly valued in Roman society.

The demand for this unusual commodity was so high that it became a commercial enterprise. Large clay pots were placed on public streets to serve as collection vats, and the contents were sold to various industries, including laundries and dentistry. The trade was so profitable that Emperor Nero instituted a tax on the collection and sale of urine in the 1st century AD. While the direct use of urine as a mouthwash eventually fell out of favor, the principle endured. The use of ammonia as a cleaning and whitening agent in dental products continued in some parts of Europe all the way into the 18th century.