You’d probably be horrified if a stranger licked your face on the subway.
But if that stranger has four legs and a tail, suddenly it’s “adorable.”
Spoiler: Your pooch’s mouth isn’t clean — it’s a petri dish with a tongue.
This is true. And I’m not kidding.
I was riding on a ferry a few days ago, and there was a guy with a nice dog sitting across from me. He pulled out a packet of little dog treats and fed one to his dog. End of story. Minus a few details.
Including some details that change the story a bit.
First, he placed the treat, which was about the size of a Cheerio, between his lips. WTF? The dog, obviously in tune with this ritual, hopped up on the seat and [ick] took the treat from the guy’s lips. I don’t have a “dog tongue-kissed owner” expression in my repertoire, but Mr. Dogtonguer obviously saw me react in some way that did not spell out “isn’t that adorable!?” A short dialogue followed:
Mr. DT: “Over the years, I’ve come to like these things. They’re quite tasty!”
Me: “Do you sniff butts too?”
Mr. DT: “Not anymore, but that’s how I met my wife.”
Me: “Same here.”
—END OF DIALOGUE—
Despite this hurl-worthy interaction, all was not lost. I had a can’t-miss article topic: It is widely thought that dog saliva is “cleaner” than human saliva. Is this really true?
Human behavior is illogical.
Let’s say that some guy on the subway leans over and licks your face. Even though New Yorkers aren’t generally known as devotees of etiquette, such an act would likely elicit a negative response from the recipient of the lick.
Yet, we routinely see people stopping to play with strangers’ dogs on the street, squealing in delight with each dose of slobber. What gives? Aren’t these two revolting scenarios pretty much the same? How is playing tonsil hockey with a bloated bulldog on 94th street acceptable while that action of the subway licker is not?
Let’s not forget that New Yorkers are some of the most neurotic life forms on earth, but not necessarily the most logical. They’ll sanitize elevator buttons with an oxygen-acetylene torch but share an ice cream cone with foofie. Is there any logic here?
It’s the type of germs, not the number of germs.
Human and dog saliva each contain about 400 species of bacteria, but the similarity ends there. The microbiome of human and dog saliva is very different.
“If you look at humans and dogs, we only saw about 15 percent that are the same species…[so], many of a dog’s mouth bacteria are less likely to be kept in check by our immune systems and native bacteria.”
Floyd Dewhirst, DDS,PHD, a bacterial geneticist at the Forsyth Institute and professor of oral medicine at Harvard University
The “science” behind the myth.
Some of the myth of the “clean dog mouth” is based on a 1990 study in the journal Physiological Behavior, which examined whether there might be any benefit to licking
“Canine saliva was tested for its bactericidal effects against pathogens relevant to the presumed hygienic functions of maternal grooming of the mammary and anogenital areas and licking of wounds. Both female and male saliva were bactericidal against Escherichia coli and Streptococcus canis but only slightly…”
So what little benefit that canine saliva might be for dogs it’s certainly going to have less (read: zero) for humans. But what else is in there? Here are a few bugs that can be transmitted from dog saliva to humans. (1)
- Pasteurella– An anaerobic bacterium (one that lives in the absence of oxygen) that can cause soft tissue infection, pneumonia, and sepsis (2).
- Capnocytophaga – A Gram-negative (3) bacterium commonly found in the saliva of dogs. Although it is usually harmless, in rare cases it can cause sepsis, which resulted in a Wisconsin man having his arms and legs amputated in 2018.
- Campylobacter – A bacterium that is one of the most common causes of food poisoning. A 2018 multistate outbreak of drug-resistant Campylobacter was traced to puppies in a pet store.
- Rabies – A viral infection that attacks the central nervous system and is fatal almost 100% of the time if the infected person is not vaccinated before symptoms begin. Dogs are the most common carriers of rabies worldwide.
Keep in mind that getting these types of infections from a dog is quite rare. Dogs have been licking faces for a long time and only rarely do we see amputations or rabies in the news. Perhaps this is one of those cases where science loses and the “ick factor” prevails.
But the following is all I need to know:
“Hookworm and roundworm is transmitted from dog to dog when they ingest one another’s stool or lick each other’s anuses…and let’s be honest, we’ve totally seen that happen.”
Sonia Batra, MD, in Prevention
Yes, we have. So I’ll leave you with some non-expert advice – unless you’re perfectly comfortable with licking dog anuses perhaps you’ll settle for simply petting Foofie’s head the next time you see him walking by on 94th street. He won’t mind. Probably.
Original photo credit: Freepik
NOTES:
(1) Transmission of these infections from dog to healthy humans are very rare; they are more of a concern to people with compromised immune systems. Infections are also more likely to be transmitted by a bite than a lick.
(2) Sepsis is a serious condition caused by pathogenic bacteria in the blood. It can lead to septic shock, which is fatal about 50% of the time.
(3) Gram-negative bacteria are harder to kill because they have an extra outer membrane that shields them from many antibiotics.
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