Dogs do not have “clean” mouths in the sense of being sterile or cleaner than humans or toilets; their mouths are full of many types of bacteria, some harmless and some potentially harmful.

Myth vs reality

  • The common saying that a dog’s mouth is cleaner than a human’s is a myth.
  • Studies and veterinary sources note that dogs carry hundreds of bacterial species in their mouths, creating a dense oral microbiome rather than a clean environment.

What’s actually in a dog’s mouth

  • Dogs’ mouths contain over 600 types of bacteria, including organisms that can contribute to gum disease and, in some cases, infections in humans (especially via bites or open wounds).
  • Many dogs regularly lick or chew dirt, feces, carcasses, and random objects, which continually introduces new microbes and parasites into their mouths.

Health risks for humans

  • For most healthy people, casual “dog kisses” on intact skin are low risk, but contact with saliva on broken skin, eyes, or the mouth can occasionally transmit infections.
  • People with weakened immune systems, very young children, or older adults should be more cautious about close contact with dog saliva.

Keeping a dog’s mouth cleaner

  • Vets recommend regular tooth brushing with dog-safe toothpaste, plus chews or diets designed for dental health, to reduce plaque, bad breath, and periodontal disease.
  • Periodontal disease affects a large majority of dogs over age three, making ongoing dental care (home care plus professional cleanings) important for their overall health.

Practical takeaways

  • Enjoy your dog, but do not assume its mouth is cleaner than yours or a toilet; treat it as “naturally dirty,” not sterile.
  • Wash hands after heavy contact with dog saliva, avoid letting dogs lick open wounds or your mouth, and schedule routine dental checkups to keep your dog healthier and their breath more tolerable.

Information gathered from public forums or data available on the internet and portrayed here.