Are Dogs’ Mouths Cleaner Than Humans’? The Real Science Behind Pet Cleanliness

You’ve probably heard someone say, “A dog’s mouth is cleaner than a human’s.” Sounds comforting, right? Especially when your dog sneaks in a quick lick on your cheek. But the truth? It’s a little more complicated than that.

Both human and dog mouths are home to hundreds of bacterial species — they just host different communities. And that’s not necessarily a bad thing. When it comes to ‘clean,’ it’s more than just bacteria — what your pet eats, how it’s cared for, and even grooming habits all play a part.
A dog that eats well, gets regular vet dental cleanings, and has its teeth brushed might actually have a healthier mouth than someone who never flosses. So maybe the real question isn’t whose mouth is cleaner, but  what makes one clean in the first place? Let’s dive in.

Are Dogs’ Mouths Cleaner Than Humans’?

People love to repeat the myth that dogs have cleaner mouths than humans, but science has already thrown a flag on that play. Dr. Colin Harvey from the University of Pennsylvania once said it best — comparing a dog’s mouth to a human’s is like comparing apples and oranges.

Each species has its own little ecosystem in there — shaped by what they eat, how they live, and even how they show affection. Scientists have discovered that dogs host around 600 types of bacteria in their mouths — not far off from humans, who have about 615. Pretty similar at first glance, right? But here’s the catch: only around 16% of those species overlap. That means about 80% of what’s living in your dog’s mouth doesn’t exist in yours at all.

Some bacterial families overlap — both humans and dogs have Porphyromonas, known to cause gum disease. In dogs, it’s usually P. gulae; in humans, P. gingivalis. Same family, different troublemakers. Both can lead to bad breath, inflammation, and tooth problems if left unchecked.

So, which wins the cleanliness contest? Truth is, both have their own mix of good and bad bacteria. Honestly, neither. Both mouths contain billions of microbes — some helpful, some not so much. In the end, what really matters is how well each one keeps up with daily care. Humans brush, floss, and see dentists; dogs rely on chews, a healthy diet, and (yes) regular teeth brushing from us. For the curious, the  American Kennel Club has an excellent explainer on this.

Which Animal Actually Has the Cleanest Mouth?

If dogs and humans tie in the “not exactly spotless” category, maybe another species takes the crown. Surprisingly, cats and even rabbits might lead the pack.

Curious about which pet truly tops the cleanliness chart? Check out our full comparison here — are cats cleaner than dogs.

A small study found that cats have fewer bacterial colonies in their mouths than dogs or humans. One experiment recorded dogs averaging about 53 colonies per saliva sample, cats about 16, and humans only around 5. Another study estimated cats host roughly 200 bacterial species — far fewer than the 600+ found in dogs and humans.

Herbivores like rabbits have clean reputations too. Because they eat fibrous plants, their mouths foster bacteria for breaking down cellulose, not protein — meaning fewer odor-causing or harmful strains. And dolphins? They’ve got nature’s mouthwash. The salt water constantly rinses their mouths, and their all-fish diet helps keep plaque-causing bacteria to a minimum.

Of course, “cleanest” doesn’t mean germ-free. Every animal’s mouth contains microbes — the key is whether those bacteria are harmful. A cat’s or rabbit’s mouth might have fewer germs, but if they bite, bacteria like Pasteurella or Capnocytophaga can still cause infections. So fewer germs doesn’t always mean safer.

Is It Safe for Dogs to Lick You?

We’ve all been there — your dog leans in for a big, sloppy kiss. It’s adorable, sure, but is it really sanitary?

For most healthy adults, dog licks are harmless. Most of the bacteria in canine saliva are non-zoonotic — they don’t spread easily to humans. The  occasional lick on intact skin is generally safe. Still, there are exceptions.

Some bacteria, like Capnocytophaga canimorsus and Pasteurella multocida, can cause infections if they reach open wounds or mucus membranes. The CDC warns that people with weakened immune systems, older adults, or children should take extra care. Dogs might also carry E. coli, Salmonella, or Giardia from outdoor sniffing or eating contaminated materials.

Nothing to panic about, though. If your dog licks your hand or cheek, just wash with mild soap and warm water. Keeping a pack of  pet cleaning wipes  handy is an easy way to clean up after cuddle sessions — especially after walks or meals. That little bit of care makes a big difference in keeping everyone healthy and comfortable.

The Cleanest Part of a Dog’s Body

Here’s something unexpected — your dog’s mouth isn’t even the cleanest spot. The nose area and back fur usually carry fewer bacteria than the mouth or paws. Paws encounter dirt and microbes everywhere, while the mouth is busy licking and chewing through daily adventures. Air circulation keeps the nose relatively clean, and fur provides a small shield against grime.

Want to keep your dog fresher between baths?

• Wipe your dog’s mouth, paws, and rear with pet-safe wipes after walks or meals.
• Brush regularly to remove dirt and distribute natural oils.
• Wash bedding and toys weekly to prevent bacterial buildup.

It’s a simple routine that helps keep your home clean and cuddles pleasant.

Practical Hygiene: How to Keep Your Pet’s Mouth Healthy

Keeping your dog’s mouth healthy doesn’t need to be complicated. Daily brushing works best — use a dog-friendly toothbrush or finger brush with canine toothpaste (never human toothpaste). Even brushing a few times a week greatly reduces plaque and bad breath.

Pressed for time? Pet safe wipes make a handy substitute. They gently remove residue and bacteria from your dog’s teeth and gums without requiring rinsing. Just wrap, wipe, and done! Many pets prefer these to toothbrushes, which makes consistency easier.

And don’t forget your cleaning tools — pet safe cleaning  wipes are great for clearing saliva, fur, or paw dirt, reducing bacteria on both your pet and your furniture. Pair that routine with a yearly vet dental checkup, and your dog’s oral health will thank you.

Final Thoughts: Clean Mouth, Healthy Pet

No mouth — not even your dog’s — is perfectly clean, and that’s perfectly fine. The secret is good habits: daily brushing, regular vet visits, and using vet-recommended products like dental chews and pet cleaning wipes. It’s simple care that makes a big difference. A clean mouth means fresh breath, fewer infections, and a happier, healthier pet. Because love may be messy — but your dog’s kisses don’t have to be!

Frequently Asked Questions (FAQ)

1. Is a dog’s mouth cleaner than a human’s?

Not really. Both contain hundreds of bacterial species — dogs around 600, humans around 615. The difference isn’t in cleanliness but in composition. Most dog bacteria are unique to them and rarely spread to humans, so “different” is a better word than “cleaner.”

2. Can dog saliva kill germs or heal wounds?

Dog saliva does contain enzymes with mild antibacterial properties, which may help them clean minor scrapes. However, it’s not sterile and can still carry pathogens. Letting dogs lick open wounds (especially human ones) is never recommended, since harmful bacteria like Pasteurella or Capnocytophaga can cause infections.

3. Are dogs’ mouths cleaner than toilets?

Despite the rumor, no — definitely not. While a clean household toilet might contain fewer live bacteria thanks to disinfectants, a dog’s mouth is constantly picking up microbes from food, toys, floors, and even feces. It’s a different kind of “dirty” — not dangerous, but not germ-free either.

4. Should I let my dog lick my face?

A quick lick on healthy skin is fine for most people, but skip it if you have cuts, weak immunity, or allergies. For safer cuddles, keep pet-safe cleaning wipes nearby to gently wipe away saliva after play or affection sessions.

5. How can I tell if my dog has poor dental health?

Watch for bad breath, excessive drooling, bleeding gums, or difficulty chewing. These may be early signs of periodontal disease. Regular brushing, dental chews, and vet checkups can prevent most problems before they start.

6. Do some animals really have cleaner mouths than dogs?

Yes! Research shows cats and rabbits tend to have fewer bacterial species, while marine mammals like dolphins stay cleaner thanks to saltwater exposure. Still, “cleaner” doesn’t mean free of germs — just different microbes, fewer harmful types.

7. What’s the cleanest part of a dog’s body?

Believe it or not, their nose and back fur often harbor fewer germs than their mouths or paws. Regularly wiping paws, brushing fur, and cleaning bedding can help keep your pup (and your home) hygienic.

8. How often should I clean my dog’s teeth?

Ideally every day — but even three times a week makes a difference. Use a dog-specific toothbrush or dog cleaningwipes designed for pets. Combine that with yearly vet dental exams for a healthy smile (and better breath).