By Dr. Becker
If you’re like many pet owners, on some level you thoroughly enjoy your dog’s sloppy kiss or your cat’s sandpaper smooch. But there’s also that little nagging voice in the back of your head reminding you that your pet’s tongue could be depositing a virtual germ farm on your face.
So is it really an unhealthy practice to let your pet lick your face?
Your pet’s mouth and digestive tract can harbor certain bacteria and parasites that can be transmitted to you and theoretically cause illness. These are known as zoonoses -- diseases that can be transmitted back and forth between humans and animals.
Bacterial Infections You Could Conceivably Get from Your Pet
A common organism found in the mouths of both dogs and cats is pasteurella, which can cause infections of the skin and lymph nodes. Bartonella henselae is a bacteria cats acquire from flea bites. Bartonella also resides in the mouth, and it can cause an infection known as cat scratch fever. In theory, you can become infected by these bacteria from your pet’s saliva.
However, most of these infections in humans are the result of bites or scratches. There is very little data pointing to a problem of transmission by pet kisses.
Intestinal bacteria commonly found in dogs and cats (regardless of the type of food they are consuming) includes E. coli, salmonella, clostridia and campylobacter. These bugs don’t cause problems in healthy pets, but they can cause intestinal disease in humans. The bacteria is present in your pet’s poop. If your dog or cat licks his bottom, he could get bacteria in his mouth, which could then be transmitted to your skin.
However, most human infections from these bacteria are the result of someone coming in contact with pet feces on their hands, and then touching their mouth or face. Little proof exists that pet kisses are a means of transmission.
Parasitic Infections You Could Conceivably Get from Your Pet
Your pet is a natural host for a variety of different parasites. If you should become infected, you could potentially acquire any number of illnesses, from skin problems to brain disease. And while these parasites may not make your pet sick, eggs passed in dog or cat poop can cause human infection. As in the case of bacteria, the primary method of transmission is fecal-oral.
However, with only a couple of exceptions, this type of infection is improbable. Parasite eggs must mature in feces or another contaminated environment in order to become infective. Your dog would have to lick your face after having contacted poop with his mouth that was from 1 to 21 days old (depending on the parasite). Because most cats aren’t poop eaters, they are even less likely to transmit a parasite infection to their owners.
The exceptions to this scenario are giardia and cryptosporidia, which are immediately infective when present in pet feces.
Benefits of Doggy Bacteria
According to a recent study at the University of Colorado-Boulder, dog owners walk around with a blend of harmless bacteria from doggy tongues (Betaproteobacteria) and paws (actinobacteria) on their skin. And believe it or not, adult dog owners share more microbes with their dogs than with their children.
The researchers noted that much of the common bacteria shared between humans and their dogs happens through licking. Their study shows that while our exposure to the larger microbial world has shrunk in modern times, and not always to our benefit, dog owners may actually have an advantage thanks to the diverse microbial community they are exposed to through contact with their canine companions. Harmless bacteria on your skin may help your immune system learn to distinguish good germs from bad.