Kate Sullivan, Allure magazine
They are prolific, disgusting, and phobia-inducing-yet they are also immunity builders. Below, some facts that will make you want to wash your hands immediately.
36 B.C.: Year Italian scholar Marcus Terentius Varro published a theory that swamps may breed illness because of "minute creatures that cannot be seen by the eyes."
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590: Year Pope Gregory I invented a post-sneeze prayer-"God bless you"-as sneezing was considered an early sign of the plague.
3: Number of times a day Henry VIII of England ordered that the walls and floors of his son Edward's rooms be washed to prevent illness. Edward died, likely of tuberculosis, at age 15.
18: Percentage of women who died in childbirth at a Viennese hospital in the seventeenth century. When Ignaz Semmelweis, an obstetrician there, made doctors wash their hands with chlorinated limewater before examining pregnant women, the mortality rate dropped to 1.5 percent.
51: Approximate number of people Mary Mallon, a.k.a. Typhoid Mary, infected with the disease during her career as a private cook. Three of those people died.
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1914: Year Listerine was first sold as an over-the-counter mouthwash to cure bad breath. It had originally been used as a surgical antiseptic, then as a floor cleaner and a potential cure for gonorrhea.
1932: Year actress Jean Harlow reportedly said of producer Howard Hughes, "One day he was eating a cookie and offered me a bite. Don't underestimate that. The poor guy's so frightened of germs, it could darn near be a proposal."
2.2 million: Approximate number of Americans who have been diagnosed with obsessive-compulsive disorder; the illness often manifests itself as extreme cleanliness.
1976: Year John Travolta starred in The Boy in the Plastic Bubble, about a teenager born with SCID (severe combined immunodeficiency).
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59: Episode of Seinfeld in which George Costanza was chastised for double-dipping a chip.
100: Miles per hour a sneeze supposedly projects mucus, according to popular belief.
35 and 39: Miles per hour that the sneezes of MythBusters hosts Adam Savage and Jamie Hyneman traveled.
67: Percentage of makeup testers contaminated with staph, strep, or E. coli on the average midweek day, according to a 2005 study.
100: Percentage that were contaminated on a Saturday, when traffic is highest at a makeup counter.
2: Percentage of contact-lens wearers who used them safely, as reported by Optometry and Vision Science in 2011. Among many violations were showering with contacts in and exposing them to unsterile water.
10 to 15: Seconds after using hand sanitizer that hands should still be wet. Otherwise, the sanitizer is insufficient, according to the CDC.
1,600: Approximate number of germs on each key at an outdoor ATM, according to a Chinese study.