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Debarking Pet Myths: A Dog’s Mouth Is Cleaner Than a Human’s

Some old wives’ tales just never seem to go away, despite scientific evidence, expert knowledge and even common sense. This month’s myth is one of those tales:

My dog’s mouth is cleaner than a human’s.

On this day that celebrates love, and knowing how many dog owners love receiving kisses from their canine companions, we thought this would be a good topic to address today.

Take a moment to think about all of your dog’s various behaviors… Despite all the butt licking, foot grooming, garbage chomping and carrion carrying done by the average dog — not to mention the lack of routine dental hygiene — is it really possible that a dog’s mouth could be cleaner than the typical human’s mouth?


According to veterinary dental specialists and veterinary microbiologists, the answer is an emphatic “no.” Some veterinary specialists consider comparing the cleanliness of dog and human mouths to be similar to comparing apples and oranges — really dirty apples and really filthy oranges. Why? Because the mouths of both dogs and people are teeming with bacteria. (There’s a reason for the terms “dog breath” and “morning breath.”) And how should “clean” be defined? Lower numbers of bacteria? Fewer disease-causing species of bacteria?

The majority of a dog’s dental bacteria (aka oral microbiome) are different from those of people. However, using DNA and RNA technology, researchers have found that a small number of bacteria (about 5 to 16 percent) live in both canine and human mouths. While scientists once thought that the different bacteria were unable to cause disease in people, they now know that’s not true. Some bacteria in dogs’ mouths can cause disease in people under the right conditions.

What’s the origin of this old wives’ tale?

The myth’s origin seems to stem from the observation that dogs lick their wounds, which enables healing with minimal, if any, infection. This observation caused some people to believe that canine saliva has some sort of healing property. They’re correct — to a point — since dog (and human) saliva has been shown to contain compounds with limited antibacterial properties. (Saliva also contains lots of other substances, including bacteria and viruses.) Veterinarians say it’s far more likely that licking helps wound healing because it removes debris and dead tissue.

The truth about a related myth

One misconception associated with the old wives’ tale that a dog’s mouth is cleaner than a human’s is the belief that wounds resulting from a human bite are more likely to become infected than those from a dog bite. This is also no longer considered true. Physicians now know that human bites occurring anywhere other than the hand have the same risk of infection as dog bites.

So should you let your pet lick you?

Since it’s Valentine’s Day — it also happens to be National Pet Dental Health Month — should you let your dog kiss you?

That depends.

Most veterinarians will say it’s fine to let your dog lick you, as long as your dog isn’t licking your face, mouth or an open sore. Infants, young children and those with compromised immune systems, however, will want to avoid sloppy wet dog kisses. For reasons why these groups should avoid such canine affection, check out this blog post by Dr. Shelley Rankin, associate professor of microbiology at the University of Pennsylvania’s School of Veterinary Medicine.

And don’t overlook this factor when considering that kiss: If your canine companion likes to sample their or other pets’ stool, you might want to rethink allowing canine kisses to the face and mouth. Regardless of your decision to let your dog kiss your face today or any other day, just be sure to wash your hands before eating or touching your eyes, mouth and face.

Happy Valentine’s Day from all of us at Diamond Pet Foods!

RELATED POST: Nine Tips for Better Pet Dental Care

The information in this blog has been developed with our veterinarian and is designed to help educate pet parents. If you have questions or concerns about your pet's health or nutrition, please talk with your veterinarian.


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