Many people may have heard a myth that dogs' mouths are cleaner than the mouths of human beings. This rumor is likely to stem from the fact that dogs are often seen licking their wounds, which rarely get infected.

However, people who believe that dogs' mouths are cleaner than humans' mouths are greatly mistaken, according to veterinarians who have spoken on the subject. Most humans have a strong belief in good hygiene, and brush their teeth at least once or twice every day. Human mouths rarely come into contact with external bacteria. Dogs' mouths, in contrast, are rarely cleaned in most cases. Dogs also have a tendency to sniff around and eat bacteria-filled waste — including rancid food and feces — whenever they are given the opportunity to do so. Contrary to popular belief, dogs' mouths are far dirtier than the mouths of the typical human being.

The reason that dogs' mouths rarely infect the wounds that they lick is that their licking has the effect of clearing away the dead tissue, similar to the work a surgeon would do to clean out a wound. Even though dogs' mouths are full of bacteria, dog bites do not usually cause infections in humans because most bacteria in dogs is particular to their species. Therefore, even if the dog is infected with a disease, the human is unlikely to catch it. For this reason, it is not especially dangerous to share food with a dog or to kiss dogs' mouths, though neither option is exactly the most hygienic of decisions.

If you are a dog owner, and would like to make your dogs' mouths cleaner, there are special toothbrushes and toothpaste that you can buy to use on your dog, which will help to get rid of some of the bacteria in your dogs' mouths. Though it may be difficult to get your dogs to open their mouths initially, they will calm down once they understand what you are doing. Some of the special toothpastes for dogs' mouths come in flavors like beef or chicken — buy one of these, and your dog will soon look forward to his daily teeth cleaning.