Is a Dog’s Mouth Cleaner Than a Human’s? Vets Weigh In

If you’ve ever shared a bite of food with your dog or let them give you a kiss directly on the lips, you aren’t alone. And maybe, like many of us, upon seeing appalled faces or hearing revolting comments, you’ve said, “It’s fine! Their mouths are cleaner than ours are!” 

We hate to break it to you, but dogs’ mouths are not cleaner than human mouths. In reality, comparing our mouths with dogs’ mouths is tricky. There are some similarities, but there are also a number of differences to take into account. So, before you go sharing a bowl, let’s dive into your pup’s mouth (and the germs found there) a little deeper. 

Is a Dog’s Mouth Cleaner Than A Human’s Mouth? 

Considering the things your dog licks, eats, or chews on — and that’s just the ones you’re aware of — it likely won’t come as a shock to hear that dogs’ mouths are not cleaner than human mouths. 

“A dog’s mouth has bacteria in it just like ours do — some species that are the same and some that are different,” says Dr. Chyrle Bonk, who has practiced in a mixed animal clinic for over 10 years. “While we both have bacteria, it’s important to mention that some dogs will eat things in their environment that aren’t considered food (feces, rotting food, etc.) which can definitely make their mouth less clean.” 

But when it comes to being “clean,” what exactly qualifies for our canine friends? 

According to Dr. Kathryn Dench determining if a dog’s mouth is clean can include “multiple factors like the absence of significant bacterial buildup, tartar, dental disease, and odor.”  

Dr. Dench explains that a dog’s mouth isn’t automatically considered dirty or unclean because it has bacteria in it. In fact, some bacteria are good. “Just like in humans, bacteria are crucial to maintaining a healthy mouth,” she says. “But bacteria become problematic if the growth isn’t balanced or controlled, leading to dental disease or infections.” 

There are other factors, such as a dog’s breed and age, that can play a role in how clean their mouths are: 

Older dogs often show more signs of dental disease due to prolonged exposure to bacteria and poor oral health habits. Over 80 percent of dogs over the age of 3 are suffering from some type of dental-related issue.  

Small breeds like Chihuahuas and Dachshunds tend to be more prone to dental issues [1]. Overcrowding of teeth in their mouths can lead to increased plaque buildup.  

Bacteria in a Dog’s Mouth vs. Bacteria in a Human’s Mouth 

While we have a similar number of bacteria in our mouths compared to dogs (615 species versus 600 species, respectively), there are different types of bacteria in each.  

This makes things tricky when it comes to comparing the two — like trying to compare apples to oranges. 

One bacterial family called Porphyromonas, however, can be found in both human and canine dental environments, specifically the two strains P. gingivalis and P. gulae. These bacterial strains are major pathogens that may lead to periodontal disease in both dogs and their owners. 

Most of the bacteria found in your dog’s mouth, however, are not zoonotic (meaning they can’t be spread between animals and people). The ones that do cause illness in people are usually transmitted by bites rather than slobbery kisses. In other words, your chance of catching something if your dog licks you is extremely low! 

However, to reduce the risk, pet parents should employ appropriate parasite prevention, vaccination protocols, and dental hygiene in their dogs. 

Is My Dog’s Mouth Actually Cleaner Than Mine? 

No, your dog’s mouth isn’t cleaner than your mouth.  

“If we look at the mouth ecosystem as a whole, dogs’ mouths are not inherently cleaner than human mouths,” says Dr. Dench. “This common myth stems from the fact that human bites are often more dangerous than dog bites due to pathogens like Staphylococcus aureus and Streptococcus species, which can lead to severe infections like cellulitis and septicemia. While dog bites can also transmit bacteria like Pasteurella and Capnocytophaga, which can cause significant infections, these tend to be less aggressive than those found in human bites.” 

We’re happy to report that the myth is officially debunked. 

You should also keep in mind if your dog has a habit of eating things they shouldn’t — like dirt, cat litter, or other dogs’ feces — it can lead to them contracting hookworms or roundworms which can be transferred to a pet parent if any contaminated saliva is ingested. 

The Importance of Cleaning Your Dog’s Mouth and Teeth 

Even if your dog doesn’t eat garbage or poop, keeping your pup’s mouth and teeth clean is essential for their overall health and wellbeing. As mentioned above, dental issues impact over 80 percent of dogs over 3 years old.  

But at-home dental care can target tartar buildup and keep a dog’s teeth, gums, and mouth healthy. A good teeth cleaning can also freshen breath – making those doggie kisses much more tolerable. 

Learning about your dog’s dirty mouth may cause you to hesitate next time they come in for a smooch. But establishing good dental care habits at home can keep your dog’s mouth clean, healthy, and happy.  

References: 

1. O’Neill, D G et al. The Journal of small animal practice vol. 62,12 (2021): 1051-1061. doi:10.1111/jsap.13405

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