Are Dogs' Mouths Cleaner Than Human Mouths?

You may have heard the claim that a dog’s mouth is “cleaner” than a human’s mouth—but it’s actually not true. 

The myth likely stems from the fact that dogs sometimes lick their wounds and heal without any infection. While that is sometimes the case, it doesn’t mean that dogs have cleaner mouths.  

Are Dogs’ Mouths Cleaner Than Human Mouths?

No. Dog mouths aren’t cleaner than human mouths. 

A 2020 study showed that while dogs and humans may have similar numbers of bacteria in their mouths, the species of bacteria are different. Some of the bacteria in a dog’s mouth may not pose a risk to human health, but others can be dangerous or even fatal to humans.  

The “cleanliness” of your dog’s mouth might vary with timing too. For example, if a dog raids a litter box, they may pick up fecal bacteria such as E. coli or Salmonella, which can cause gastrointestinal illness. And if they eat spoiled food, they could be exposed to bacteria that can lead to vomiting or diarrhea. 

How Dog Mouths Differ From Human Mouths

There are two major differences between a dog’s mouth and a human’s mouth when it comes to cleanliness: pathogens and behavior. Pathogens, in simple terms, are germs that can cause a disease.  

Dogs Have Different Pathogens in Their Mouths 

Exact amounts can vary, but one recent paper found that dogs had 714 types of bacteria in their mouth. In contrast, the National Institutes of Health says that human mouths contain around 700 types.   

Many of these microorganisms are unique to either dogs or humans.  

As a result, bacteria that may not cause health problems in dogs may be harmful to people. 

For example, Capnocytophaga canimorsus, a bacterium commonly found in dog saliva, can be dangerous to humans if it comes into contact with a minor wound—from a dog licking it, for example. 

While rare, there have been documented cases of people developing septicemia (also known as blood poisoning) from it.   

Dogs Use Their Mouths Differently Than Humans  

Dogs also explore their world using their mouths. They lick, chew, and eat things they find in their environment and may drink from untreated water sources like puddles or streams. All of this exposes them to bacteria and other potential pathogens that people typically don’t encounter. 

These behaviors don’t necessarily make dog mouths “dirty,” but they increase the chance that your dog’s mouth may be harboring pathogens that could make you sick. 

Why Human Mouths Are Often Healthier

Human mouths are often healthier than dogs’ mouths because we maintain them more consistently. Most people brush, floss, and receive professional dental cleanings—care that many dogs don’t routinely get. 

As a result, by the time they are 2 years old, around 80% of dogs have periodontal disease, a condition associated with bacterial infections. A dog’s oral health should always be evaluated by a veterinarian.   

Is Dog Saliva Safe for Humans?

Dog mouths are home to lots of bacteria and other potential pathogens, but a dog’s saliva poses minimal risk for adults with healthy immune systems.  

However, for some people the risk is higher: 

• People who are immunocompromised  

• Infants and young children with immature immune systems 

• Older adults with weakened immunity 

• Anyone with cuts, scratches, or skin wounds that allow bacteria to enter the body 

Rabies is a fatal disease that can be spread through saliva, so if you suspect a dog has been exposed to or has rabies, keep your distance and contact a veterinarian and your own doctor immediately for instructions.  

Is It OK To Let Your Dog Lick You?

An occasional lick is usually OK if you and your dog are healthy and you don’t have any cuts. If you’re worried, you can always wash the area with soap and water afterward as a precaution.  

Never let your dog lick you near your eyes, around your mouth, or close to an open wound. These areas provide easy access to mucous membranes or the bloodstream, increasing the chance of infection.  

How To Keep Your Dog’s Mouth Clean

Maintaining your dog’s oral care won’t remove all pathogens from their mouth, but it is an important part of a healthy dog’s routine.   

There are a few ways that you can optimize your dog’s oral health.  

Daily Tooth Brushing 

Brushing your dog’s teeth every day is the best way to prevent periodontal disease.  

Use a soft-bristled toothbrush and toothpaste formulated for dogs, like those found in the Virbac C.E.T. Enzymatic Oral Hygiene Poultry Flavor Dog Dental Kit.  

If daily brushing isn’t possible, brushing a few times per week is still beneficial. 

Other Forms of Home Dental Care  

Products approved by the Veterinary Oral Health Council (VOHC) can help reduce the formation of bacteria-laden plaque and tartar in your dog’s mouth. It’s best to use them in tandem with regular brushing at home.  

• Dental chews and treats: Try Purina Pro Plan Veterinary Diets Dental Chewz or Greenies Regular Natural Original Chicken Flavor Dental Dog Treats. 

• Dental diets: Pick one formulated for a dog’s oral care, like Hill's Science Diet Adult Oral Care Chicken, Rice & Barley Recipe Dry Dog Food. Ask your vet before switching your dog’s diet. 

• Powders and water additives: ProDen PlaqueOff Powder and TropiClean Fresh Breath Dental Water Additive for Dogs are vet-approved options.  

Professional Dental Cleanings 

Even with excellent home care, most dogs need periodic dental cleanings under anesthesia. Your veterinarian can recommend a schedule based on your dog’s oral health.