Well, it looks like there really is such as thing as a dog person.
Humans who share their homes with canines also share the similar bacterial houseguests on their skin, ecologists reported Tuesday in the journal eLIFE.
In fact, two dog owners who don't even know each other have about as many of the skin bacteria in common as a married couple living together.
The signature doggie blend is a mixture of harmless bacteria from their tongues and paws, the report finds. Microbial sharing from pooch to person occurs primarily through two routes: tongue to skin and paw to skin.
That's right, dog owners have bacteria from Fido's tongue and paws flourishing all over their bodies.
There wasn't an analogous germ signature for cat owners, the scientists say. Cats are more selfish?
Dogs, cats and people are all coated in microscopic critters. They cover our skin, grow in our mouths and completely dominate parts of the gut. Your body has about 10 times more bacterial cells than human cells and up to a thousand different species.
Collectively, this microscopic zoo is called the microbiome. And it plays a critical role in human health. It helps to set your metabolism, fine-tune your immune system and even freshen (or sour) your breath.
To see how canine cohabitation could alter the species in this zoo, Rob Knight and his team at the University of Colorado, Boulder, characterized the bacteria shacking up with 60 families – 25 of them had at least one dog, including big breeds, like German shepherds, Labrador retrievers and huskies.
The scientists took samples from each inhabitant's forehead, palms or paws, tongues and poo. They then sequenced the DNA in each sample to determine which species of bacteria were living there.
Humans living together shared similar bacteria at all three body sites: skin, mouth and gut. But for dogs, it was all about the skin.
Two types of pooch bacteria were flourishing on dog owners' skins: Betaproteobacteria, a group of critters that hang out on dogs' tongues, and actinobacteria, which live in soil and like to nestle in the nooks of dogs' paws.
These findings are "consistent with a common occurrence of oral–skin transfer between dogs and their owners," the authors write.
Looks like, all those slurpy dog kisses really do have a long-lasting effect on your skin's ecology.
Could they also affect your health?
This study can't say. But we do know that innocuous bacteria on the skin help the immune systems learn the difference between good and bad germs. And allergies can crop up when this ability short circuits.
Recent studies have even linked up contact with pets when we're young with a decreased risk of allergies and autoimmune disorders later in life.
Now if you'll excuse me, I need to go snuggle up with my very stinky German shepherd.