There are few things dogs love more than giving big, sloppy kisses. If you grew up around dogs, you’ve probably heard the old wives’ tale that dog mouths are cleaner than humans. This is a reassuring thought when dealing with pups who love to lick—but is it actually true?

According to an animal behaviorist, dogs lick their humans as a sign of affection. But when they’re doing the licking, are our pets leaving behind a trail of dangerous bacteria?

Are dog mouths cleaner than humans’?

In order to get to the bottom of this age-old tale, researchers from Oklahoma swabbed the mouths of humans, dogs, and cats. Then, they analyzed the swabs for the number of bacteria in each sample. Their conclusion? Human mouths had the smallest number of bacteria, followed by dogs and then cats. In other words, human mouths are slightly less dirty than dog mouths are.

At the same time, research suggests that dog mouths are much less likely to spread disease to humans. This is because dog bacteria and human bacteria thrive in different environments. When you get a kiss from another human, their bacteria can easily repopulate. It’s much harder to pass bacteria from dogs to humans, and vice versa.

How to keep your dog’s mouth clean

Even with this information, there’s much we can do to keep dog mouths cleaner. Here are a few doggy dental hygiene tips:

1. Brush their teeth

Just like humans, dogs can benefit from brushing their teeth. Studies show that brushing your dog’s teeth inhibits the growth of mouth bacteria—as long as you use toothpaste made for dogs.

Not sure how to start brushing? According to associate veterinarian Morgen Deramus, approach it just like you’d approach any other training. Use positive reinforcement, go slowly, and be patient.

Start by giving your dog a taste of pet toothpaste and then giving him a treat. Then introduce toothpaste on a toothbrush into your dog’s mouth and give him a treat. Eventually, you may be able to brush your dog’s teeth without any stress or fuss.

Of course, some dogs are still fussy with this process. If it’s not easy to train your dog to enjoy brushing his teeth, try chew treats.

2. Chew treats

Plaque is a major dirty mouth culprit. In order to cut down on your pup’s plaque, researchers suggest giving them dental chews daily. Treats your pet can gnaw on do a great job of reducing plaque buildup.

There’s a wide array of chew treats on the market, from minty fresh options to natural chews. From antler chews to braided bully sticks, there are dental health solutions out there that your dog is sure to love.

3. Go in for a professional cleaning

If your dog’s breath is extra funky, it’s always a good idea to bring them to the vet for a teeth cleaning. Veterinarians know exactly what’s going on in your dog’s mouth, and they should be your first call if you’re ever in doubt.

Want to learn more pet tips? Visit our blog. And if you're curious about other dog facts you might've got wrong, read this.