In Roman times, the ancient Gauls, as well as other people, used urine (which contained urea) as a mouth rinse in order to whiten their teeth.
In fact, “urine therapy” — strange as it may sound — is still promoted in certain alternative medicine circles.  Various applications of human urine is promoted for medicinal or cosmetic purposes, including the drinking of one’s own urine and massaging one’s skin with one’s own urine. While there is currently insufficient evidence for the therapeutic use of urine, many chemical components of urine have wide-scale industrial and agricultural use, such as urea and urokinase.