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Myth Buster: Dogs' Mouths Aren't Cleaner Than Ours

People often say that dogs’ mouths are cleaner than humans’, but that isn’t really true. A dog's mouth isn't necessarily cleaner than a human's. Instead, it contains a different type of bacteria. Some bacteria are found in both dog and human mouths, but many are different.

(Photo via Shutterstock)

That means getting bit or even licked by a dog or cat can be dangerous, especially if you have broken skin from a cut or scrape.

Need proof that our pets’ mouths are just as dirty as ours? Between 10 percent and 15 percent of dog bites become infected, and about half of cat bites do. Some of these infections can be serious, and in very rare cases even deadly.

The different organisms that live in a species' mouth is called its oral microbiome. A human's oral microbiome includes between 400 and 500 species of bacteria. Dogs have an oral microbiome of about 400 bacterial species, while cats have at least 200, but more types will likely be identified in cats and dogs as more research is done.

Between humans and dogs, about 15 percent of the oral microbiome is the same. That means the majority of bacteria species found in humans and dogs are different.

The idea that dogs' mouths are cleaner than ours may stem from the fact that most diseases are not easily passed between us and our pets. We can't give our dogs the flu, and we don't get canine illnesses like kennel cough from our dogs. That's because these illnesses are not able to be passed on from humans to other species and vice versa. There are some exceptions to this, including COVID-19. A small number of pets worldwide have been reported to have contracted the virus that causes COVID-19 after close contact with people who have tested positive for the coronavirus.

Another popular idea about dogs and their saliva is that letting a dog lick a wound can help it heal faster. This idea has been around for centuries, dating back to ancient Greece. It's also true that most mammals lick their wounds.

Saliva does have some healing properties, but not just dog saliva. Saliva from humans and other mammals, including dogs, contain proteins called histatins, which can help prevent infection. Saliva also contains molecules called peptides that have antibacterial properties.

For animals, the act of licking a wound can be beneficial, because it removes dirt and debris from the area. This helps lower the risk of infection.

None of this, though, means that letting a dog lick your wound is a good idea. Or that even a very minor dog or cat bite isn't at risk of becoming infected. In most cases, these acts are harmless, but very rarely it can cause serious infections in people.

If you get bit by a dog, have an adult help you clean the bite area. Wash the area with mild soap and warm water immediately. Let water wash over the wound area for five or 10 minutes, then dry it carefully and apply an antibiotic ointment before covering the area with a bandage. If it is a deep puncture wound, if the skin is badly torn or if the wound is bleeding profusely, seek medical attention.

Most cases of being licked by a dog are no cause for concern for people with healthy immune systems, but it's still a good idea to practice good, basic hygiene. If you get licked, wash the area with soap and warm water.


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