Is a dogs mouth cleaner than a humans mouth?

[Yamaneko]

Would you rather be bitten by a dog or by a human? Well, neither of course, but if you had to choose, which would it be? According to a widespread notion, a dog bite is the better choice since a canine mouth is cleaner than a human mouth.

Is this true? Well, yes and no. When we talk about the cleanliness of a mouth, we're really talking about the amount and type of bacteria it contains. The kind of bacteria found in a human mouth and a dog mouth depend on what's been there recently. Unlike dogs, humans typically do not eat raw meat, garbage, and small animals in various states of decay. Given a dog that just locked its jaws around a decomposing squirrel, we might say that the dog's mouth is, for the moment, less clean than a human mouth that has not recently housed a dead squirrel. And since the squirrel-eating dog may pick up disease-causing bacteria from the dead animal, a bite from that dog may pass on dangerous germs.

But insofar as a clean mouth means one that is less likely to cause disease, consider that germs tend to be species specific. Harmful dog germs are usually harmless for humans, unless we're talking about rabies, a disease that affects dogs and people in equally damaging ways. But generally, humans are immune to most dog germs. Likewise, human germs probably won't harm a dog. But human germs can harm humans, of course. So a bite from a human mouth full of harmful bacteria may very well be more damaging than a dog bite, even if the dog's mouth is full of harmful dog germs.