Is it risky to let your dog lick you? The truth about dogs' mouths being cleaner than humans'

• The bacteria in dogs' mouths usually cannot infect humans because it is incompatible.
• But there are a few germs — like salmonella and rabies — that you can get from dog saliva.

Dogs get their mouths on all sorts of objects from an old pair of sneakers in the back of your closet to the kitchen trash under the sink. But even with their interest in items that humans may consider dirty, you've likely heard that a dog's mouth is actually cleaner than a human's.

It turns out this common saying is actually a myth, says Dr. Andrew Karmin, Chief of Staff at URvet Care. Your dog's mouth is not cleaner than your own, but there are ways to care for your dog's mouth and reduce their risk of disease regardless of how much they are poking around in the garbage.

Are dogs' mouths cleaner than humans?

The short answer is no, dogs' mouths are not cleaner than humans. But, this also isn't exactly a fair comparison.

Both human and dog mouths contain hundreds of microorganisms and bacteria, Karmin says. Most — but not all — of the bacteria in your dogs mouth are zoonotic, meaning that they can only infect other dogs.

For example, you won't get a cold from letting your dog lick your cheek, but you might from coming into close contact with a sick human. In this way, sharing a kiss with your pooch is usually less risky than kissing another person.

But just because your dog is much less likely to spread harmful germs, doesn't mean that their mouth is actually clean.

The biggest difference in cleanliness between dog and human mouths is that humans practice regular oral hygiene with daily teeth brushing and flossing, says Dr. Celia Friedman Cowan, Director of Veterinary Medicine for Koala Health, an online pet health company.

Some types of bacteria that cause periodontal disease, or gum infection, can be found in both dog and human mouths, but because dogs' teeth are not brushed or flossed as often, they have higher rates of dental disease.

In fact, dental disease is the most commonly diagnosed disease in dogs, affecting more than 80 percent of dogs over the age of three.

Can dog's saliva heal wounds?

Another common saying about dogs' mouths is that their saliva can help heal wounds. This is partially true, but with some caveats, says Dr. Jamie Whittenburg, a veterinarian at SeniorTailWagger.com and director of Kingsgate Animal Hospital.

Both human and dog saliva have some antibacterial properties, including proteins called histatins that can help prevent infection.

However, this effect only extends to a few select bacteria typestypically found in the oral cavitiy, like streptococcus. And with hundreds of types of bacteria present in the saliva, it's more likely for dog saliva to cause an infection than clear one, Whittenburg says.

"A dog's mouth is like their hands and fingers, used to poke, prod, scratch, and pick things up, " Friedman Cowan says. "Everything goes in their mouth, including gross stuff."

What diseases can you get from dog saliva?

One reason why the myth that dogs' mouths are cleaner than humans has likely stuck around is because dogs and humans don't typically spread disease to each other by swapping saliva.

You can get sick however if your dog's saliva comes into contact with an open wound or broken skin, Karmin says.

Illnesses you can get from dog saliva include:

• Rabies. This is a viral disease that attacks the brain and spinal cord. It is nearly always fatal.
• Brucella. This is an infectious disease that can cause fever and body aches. It is treated with antibiotics.
• Pasteurella. This illness typically occurs after a dog bite or scratch and causes tenderness, pain, swelling, and drainage in the affected area.
• Capnocytophaga. This is a germ that lives in the mouths of cats and dogs. It does not make animals sick but can cause serious infections in humans.
• Salmonella. Dogs that eat raw diets are also at a higher risk of contracting Salmonella, which can be passed along to humans.

How to reduce your dog's risk of disease

It's impossible to keep any mouth completely germ-free, including your dog's. But there are ways you can protect your dog's oral health and reduce their risk of disease. Here are some tips for keeping your dog's mouth healthy:

• Brush your dog's teeth at least once a week with a finger brush or dental wipe.
• Have your dog's mouth regularly examined by a veterinarian, about once a year.
• Take your dog for professional veterinarian teeth cleanings. These may be once a year for most dogs, though some breeds, like Bulldogs and Yorkshire Terriers, may require more frequent cleanings.
• Provide soft chew toys that you can indent with your thumbnail. Toys that are too hard can increase the risk of painful tooth fractures that may become infected, Friedman Cowan says.
• Give your dog dental chews to nibble on. These can be found in pet stores and are designed specifically to help clean your dog's teeth and minimize built-up plaque and tartar.

Insider's takeaway

The saying that a dog's mouth is cleaner than a human's is a myth. Both human and dog mouths contain hundreds of microorganisms and bacteria. Some of these microbes overlap between the two species, but many of them are different, making comparing dog mouths to human mouths tricky.

It is possible to get sick from a dog's saliva, but only if it comes into contact with an open wound or broken skin. You can help keep your dog's mouth healthy by brushing their teeth once a week and taking them for regular professional teeth cleanings at the vet.