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Your skin microbes prove you're a 'dog person'

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By Meghan Holohan, NBC News contributor

If you’re a dog person, you may have more in common with your fellow dog owners than you even realize. 

New research shows that two strangers who both own dogs are more likely to share similar skin bacteria than a married couple without a dog in the home. The study also found that dogs have more skin bugs in common with their human owner than other dogs.

Researchers examined the skin of people who lived together – couples, couples with dogs, couples with children and couples with children and dogs – and found that the family dog very generously shares his skin bugs with his owners. The groups with dogs in the home shared more skin bacteria than any of the other cohabitating groups studied. Not surprisingly, doggy affection is behind all this sharing – dogs transmit their skin microbes to their people via tongue-to-skin, skin-to-skin or paw-to-skin contact.

If you’re not a dog person, you might find all of this a little gross. But remember, our skin is already teeming with thousands of kinds of bacteria, and those microbial colonies help keep us healthy by bolstering our immune systems or aiding digestion, for example. Plus, the researchers assure that picking up some doggy bacteria is not harmful to humans.

“Most of the dogs’ [microbes] will be more beneficial than harmful,” says Rob Knight, a co-author of the new report and an associate professor at the University of Colorado, Boulder. He points out that past studies have shown that kids who grow up with a dog in the home have lower rates of asthma and allergies.

Knight and his colleagues wanted to find out how cohabitating couples spread microbes, and if they contributed to each other’s microbiome – that’s the entire collection of microorganisms living in an environment (in this case, our bodies). They took oral, skin, and fecal samples from 159 people: 17 families with cohabitating children from six months to 18 years old; 17 families with one or more dogs but no children; eight families with both children and canines; and 18 families with no dogs or kids. The researchers also took samples oral, skin, and fecal samples from the dogs. They then analyzed all the samples to see how much overlap existed.  

He suspected that couples with young children would have the most microbes in common; kids seem like a hotbed of microbes and caring for them means couples face the same exposure. But that’s not the case – families with canine family members shared more microbes. Interestingly, the same isn't true for cat owners, possibly because our feline friends are less social. (Besides, everyone knows cats hate sharing.) When Spot bestows a lick of love, he’s also giving a gift of betaproteobacteria, and when he offers a paw shake it comes with a side of actinobacteria. These two doggy microbes were most often found on their owners’ skin.    

Even though the dog-human microbial bond is strong, Knight notes that families show evidence of having similar microbiomes. Even still, each person’s microbial makeup is singular. 

“It is fascinating how different and unique that the microbial communities on people are,” he says.

While it might make our skin crawl to consider that we have something like 100 trillion microbes in and on our bodies compared to our 10 trillion cells, Knight assures us that microbes are friendly.

“Microbes are actually helpful,” he says. “If most of the microbes were out to get us, we’d really be in trouble.”

The study appears at the online journal eLife. And if you're interested in participating in research mapping human microbes, sign up here.