Is Dog Spit Cleaner Than People Spit?
He licks his butt, drinks out of the toilet and eats out of the trash. By all means, let your dog slurp on your face. He sounds like a regular clean freak.
Caroline Coile |
Posted: September 8, 2014, 6 a.m. PST
But how many times have you heard that his mouth is cleaner than yours? I don't know where your mouth has been, but I'm thinking, no.
The idea may be based on a couple of observations. First, dogs lick their wounds. These wounds eventually get well, and to some extent, may possibly be helped in their healing by the licking. Most of its benefit is likely because the licking stimulates blood flow, which encourages healing, and because it removes dead tissue, sort of like debriding a wound. But there may be more to it. Researchers have found saliva contains histadins and nitrite, which ward off infection, and nerve growth factor, which accelerates healing. But spit is probably not the best way to get these healers, because spit also has bad things in it.
Both dogs and humans have bacteria-filled mouths. Some of the bacteria is the same, some is different. Some is harmless, some is not. Dog bites get infected. So do human bites. And it may be that the early literature that found that human bites got infected more than dog bites also fed the notion that a dog's mouth is cleaner than a human's. But when the data was re-examined, it turns out that the type of human bites that are more infected are the ones that somebody gets on their fist when punching somebody else in the mouth. Human bites on any other part of the body are no more likely to get infected than dog bites. Both bites should be thoroughly cleaned.
It is true that you're more likely to catch an illness from kissing a person than kissing a dog. That's because so many illnesses, like colds, flu and strept throats are species-specific. That doesn't make the dog's mouth necessarily cleaner. After all, they're more likely to catch something by kissing another dog compared to a human. But some people have gotten sick from kissing a dog after the dog has eaten something to which dogs are comparatively impervious. Salmonella, for example, has been found in dog treats and food on occasion. The dogs that ate it seemed perfectly fine; the people who kissed them right after they ate it got salmonella!
What we need, of course, is hard evidence. On the popular Mythbusters television series (OK, not exactly HARD evidence, but...), the stars found more bacteria in a sample taken from a human mouth than from a dog mouth. At least one YouTube video from a student science project found the opposite.
Yet another had inconclusive results.
In fact, there are loads of home-based small experiments but none of them seem to agree!
This student project at amnh,org probably has the best data I've found. The author of the study found that humans had slightly more bacteria than dogs, but dogs had a greater diversity. This diversity included gram-negative bacteria, which is more likely found in fecal matter. Probably because they lick their butts!
Regardless, it's not so much the quantity as the quality. Some bacteria is totally harmless, so unless you know what bacteria you're counting it doesn't really matter. Nobody expected anyone's mouth to be aseptic.
The bottom line? Keep your dog's mouth as clean as possible. Brush his teeth to prevent gum disease and infection. Close the toilet lid. Put away the trash. But go ahead, live life on the edge: Give your dog a kiss on the snout!
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