A new study of the bacteria living on family members and their dogs revealed some surprises in the way microbes are shared within a household.
"One of the biggest surprises was that we could detect such a strong connection between their owners and pets," Rob Knight, a researcher at the University of Colorado Boulder, said in a statement. "In fact, the microbial connection seems to be stronger between parents and family dogs than between parents and their children." 
By swabbing tongues, foreheads, feces, palms and paws, Knight and his colleagues collectedsamples from 60 families, including 17 households with children, involving 159 people and 36 dogs in total.
Overall, the researchers' findings showed that the people and theircan greatly influence the microbes that live in the body. Sharing surfaces (countertops, doorknobs, you name it) and breathing the same indoor air seems to make it much easier for family members to swap skin microbes than tongue or gut bacteria in a home, the scientists say. And pets are part of the exchange.
"Ourin particular seems to be the most malleable by our immediate surroundings, which includes the presence of household pets," study researcher Se Jin Song, a CU-Boulder doctoral student, said in a statement. Couples who had a dog shared more skin bacteria with each other than couples without a canine companion, the researchers found.
Meanwhile, parents seemed to have much more tongue and gut bacteria in common with their own children than with other children, but only after about age 3. (Kids are not born with a built-in , but acquire most of it by age 3.) The foreheads and palms of fathers and their infants had the weakest microbial connection of all the body sites and relationships studied by the researchers.
Microbes vastly outnumber human cells in the body. Whereas some kinds of bacteria can make you sick, others are vital for various aspects of a person's health. Gut microbes, for example, can help to digest food, make vitamins and fight off disease.
The new study, which was detailed online today (April 17) in the open-access journal , adds to previous research showing that the makeup of human bacteria is affected by factors like environmental exposure. For example, the "," first put forth in the 1980s, posits that exposure to bacteria and other microorganisms can help bolster immunity to environmental antigens, cutting the risk of asthma and food allergies. There's more and more evidence that pets could play a role in this process.
"Recent studies link early exposure to pets to decreased prevalence of allergies, respiratory conditions and other immune disorders in later stages of development, and skin microbes in particular are now receiving more focus as important players in immune regulation," the researchers wrote.
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