A closer look

This frankly bizarre myth needs to die. Dog mouths and human mouths both contain roughly 600 different types of bacteria, they are just different species of bacteria. So while a dog's saliva might not contain human-specific germs, it is absolutely crawling with canine pathogens. Considering dogs greet each other by sniffing rears and regularly eat literal garbage, letting them kiss you on the mouth is biologically reckless.