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You had bad info in your last column: Urine is not sterile. Further, though it is true the mouth and saliva can fend off some pathogens, tiny tears and abrasions in the oral mucosa can lead to herpes infections, esophageal cancer, and even HIV. —Robert B.
For those just tuning in, last week's column responded to a question suggesting men shouldn't have to wash their hands after urinating. The questioner invoked the idea of sterile urine to support his argument, and I—erroneously, painfully—confirmed his assumption. Busted!
Sterile urine is one of those things everybody over a certain age learned about in school that later turned out to be wrong. (This category also includes the brontosaurus, the map purporting to show which parts of the tongue are sensitive to which tastes, and historical accounts of America portraying white Europeans as the good guys.)
The truth is that healthy urine (mmm!), when cultured in a lab, has a bacterial content below the threshold necessary to confirm an infection ("culture-negative" is the term of art), which is probably how the myth started.
That said, the threshold in question is 100,000 organisms per milliliter, which is not exactly squeaky clean.
Talk then turned—as it so often does—to the microbial content of the penis writ large. Apparently last week's microbiologists erred in assuring us that, even though that organ is too filthy to touch, it's totally OK to stick in your mouth.
As Robert points out, recent studies suggest HPV—long known as a cause of cervical cancer in women—is now turning up in young men's gullets as a risk factor for esophageal cancer. There's other stuff, too. The mouth remains the safest of the body's three major phallic docking sites, but it's not risk-free.
To sum up: (a) Human genitalia are every bit as dangerously germ-ridden as Mother always said, and (b) washing them in urine won't help. Dr. Know regrets the error.