Are Dogs' Mouths Clean? The Messy Truth Behind the Myth
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The thing was, five minutes earlier, I caught her outside absolutely going to town on what looked like a dead bird. She crunched down, wagged her tail, looked right at me. Forty seconds after that, she sprinted into the house like nothing happened, leapt on the couch, and—bam—gave my face a full tongue bath.
I sat there, feeling weirdly honored and totally grossed out, and wondered: Are dogs' mouths really clean? Or did my face just turn into a giant Petri dish?
First, let’s get one thing out of the way: I am not a scientist. (If I were, I’d probably wear gloves to play fetch.) But this old “a dog’s mouth is cleaner than a human’s” thing? I’ve heard it forever, and honestly, I wanted to know if my childhood self was right to let dogs lick my popsicle.
So I looked it up. Turns out, dog mouths are like tiny wilderness ecosystems—wild, mysterious, and full of stuff you don’t necessarily want on your sandwich. But somehow, no one online seems to agree on how gross (or not) it really is.
Here’s what we found when we stopped and gave it a sniff. (Not literally. Well, not after the bird incident.)
Key Takeaways
- Not cleaner—just different. Dog mouths aren’t cleaner than humans, just a whole other breed of messy.
- Loads of bacteria. Dogs and humans have about the same number of bacteria species but not the same kind.
- Your dog eats weirder stuff. Dead birds, socks, trash—you name it. All that adventure ends up in their mouth.
- Dog saliva can carry risks. Most of the time it’s harmless, but some dog mouth bacteria can infect humans.
- Dog kisses: mostly safe-ish. Licking your skin is rarely an issue, but open cuts? That’s another story. Wash up if it happens.
Going Down the Dog Mouth Rabbit Hole
Why Do People Think Dog Mouths Are Clean?
First thing I found: apparently, this myth goes way back. Some people even say it started with ancient Greeks thinking dog saliva could heal wounds. (I’d love to see their reaction to Daisy’s post-trash dive breath.)
But maybe it’s just wishful thinking. I mean, dogs will literally eat goose poop and then lick grandma right on the lips. We want to believe their mouths are magic because it makes their grossness feel less… gross.
All I know is, the phrase 'cleaner than a human mouth' works better as a comfort blanket than a science fact.
What Actually Lives in a Dog's Mouth?
Turns out, dogs have about 600 different types of bacteria hanging out in their mouths. Sounds a lot like humans… except totally different bacteria.
A bunch of these are dog-only germs like Porphyromonas gulae (yeah, I can’t pronounce it either) and Capnocytophaga canimorsus. Fun fact: some of these can cause doggy gum disease and, if bitten or licked on an open cut, they can mess with humans too.
Your dog’s mouth is like a weird science project that never got cleaned out from last semester—always changing, always full of surprises.
Are Dogs' Mouths Cleaner Than Humans'?
The answer: nope. We might have similar bacteria numbers, but that’s where the similarities end. If you swapped spit, you’d both probably be pretty unhappy.
Also: most people brush their teeth at least twice a day. Most dogs? Maybe once a year at the vet—with a lot of bribery and possible wrestling.
There’s simply no trophy for 'cleanest mouth.' It’s apples and oranges. Or, honestly, apples and moldy tennis balls.
Honestly, these do more for my dog’s breath than anything else that doesn’t require wrestling.
See on Amazon →Is Dog Saliva Actually Dangerous?
Most of the time, letting your dog lick your hand or your face isn’t going to hospitalize you. (After the dead bird? I did wash up, just in case...)
But here’s the real deal: those unique dog germs CAN infect humans—they’re called zoonotic bacteria. Most of us will never notice, but kids, the elderly, and folks with weak immune systems should watch out.
Those rare 'flesh-eating bacteria' stories you see on the news? Usually it’s a combo of bad luck and bad timing. But it happens.
How Dirty Is a Dog's Mouth Really?
Here’s the list: plaque, tartar, leftover bits of kibble, bacteria, and—if you have a dog like mine—whatever he found in the driveway this morning.
If a dog’s breath smells like a haunted mop, you can pretty much bet their mouth isn’t a sparkling clean fish tank.
Vets recommend brushing dog teeth, not because it’s fun, but because bacteria build-up in there can lead to dental disease, infections, or worse.
So What’s Up With Dog Saliva?
Dog spit isn’t full of miracle healing powers. Some old legends got started because dogs lick their wounds and seem to bounce back.
Turns out, their bodies are just better at handling their own bacteria—not yours. Licking might help clean a cut, but it also introduces germs.
Bottom line: dog saliva is a cleaning system—for dogs.
Distract your dog from licking stuff they shouldn’t (like roadkill) with something actually safe. My sanity-saver.
See on Amazon →Can I Let My Dog Lick My Face?
I do. People will judge. Sometimes I regret it (see: bird mouth). For most healthy dog owners, a dog licking your cheek or even your lips isn’t the end of the world.
But I’m not sharing ice cream cones or letting him go near paper cuts. And if a dog licks your bloody knee or gets up in your nose? Wash up.
If you’re immunocompromised or just squeamish, keep face kisses to a minimum.
What’s the Deal with Dog Mouth vs. Human Mouth?
Human saliva is mostly water, plus a little amylase for breaking down starches. Dog saliva? Not much amylase. It’s thicker, stringier, and sometimes foamy (especially love that for my jeans).
They also don’t get cavities like us—but they DO get gum disease and tooth rot. Honestly, both species’ mouths are kind of gross, just adapted to different diets and habits.
If you swapped saliva with your dog, you’d probably both freak out. And then need to call a doctor. So maybe don’t.
Curious what your dog licks while you’re gone? (Warning: you can’t unsee it.) Great for mystery-solving.
See on Amazon →Could You Run Your Own Science Fair Project?
Apparently, kids actually test this old myth for school. (My money’s on 'disgusting results' every time.)
Swab a dog’s mouth, swab your own, grow colonies on petri dishes. The grossest one wins! But it’s never clear-cut, since it’s not about numbers, but types of germs.
One thing’s for sure: you will never want to let your dog lick your open wound again after seeing the results.
How Clean *Should* Your Dog's Mouth Be?
Nobody is brushing their dog’s teeth twice a day unless they have a medal-worthy routine and a very trusting dog. I get it. But skipping dental care? That actually IS risky—for them, not you.
Try dental chews (my dog prefers the ones shaped like tiny alligators), brush every now and then, and definitely, DEFINITELY get weird smells checked by a vet.
Living with dogs means accepting a certain amount of mystery bacteria. It’s part of the deal—and part of the fun.
Let's Get Gross, Together
You ever catch your dog eating something you *wish* you could unsee? (Especially knowing where that tongue’s been...) We’re collecting real, weird, and hilarious stories from the GREET Dog crew.
What’s the wildest thing your dog’s licked, and did you let them kiss you afterward?
Frequently Asked Questions
What part of a dog is the cleanest?
Honestly, probably their fur right after a bath, before they roll on anything. Their mouths? Definitely not the cleanest.
What animals have the cleanest mouths?
If you find one, let me know. Some say sharks or cats, but pretty much every animal mouth harbors its own weird bacteria.
How clean is a dog's saliva?
Not sterile, not 'healing.' It’s just full of dog-specific germs. Not usually a big deal, but not soap either.
What is the difference between human and dog saliva?
Humans have more enzymes for digesting carbs; dogs have thicker, stickier saliva. And way different bacteria.
Is it OK to let your dog lick your face?
Mostly yes, if you’re healthy and don’t have open wounds or a weak immune system. Wash up after if you’re worried.
Can dog mouths be dangerous for humans?
Yes, rarely—dog bites or deep licks on wounds can transmit some unique bacteria. It’s not common, but possible.
Are dog mouths cleaner than toilets?
Honestly, that depends how often you clean your toilet. But no, dog mouths aren’t magically sanitized.
Are dog mouths cleaner than cats?
Not really. Both are packed with different types of bacteria—neither is winning any hygiene awards.
So, no, your dog’s mouth isn’t some magical, germ-free sanctuary.
But it is full of stories, mischief, and a whole history of that muddy backyard adventure.
If you want cleaner kisses, wipe their mouth and maybe brush their teeth—sometimes.
Or learn to love the messiness. (It won’t kill you… probably.)
Either way, you and your dog are in this gross, wonderful world together.
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