If you think your home is a refuge from the gross bacteria of the world, a new study published in Science will burst your antibacterial bubble. Every room in your house teems with bacteria so unique to you and your family that a swab of any room reveals your microbial signature.
Scientists involved in the Home Microbiome Project sequenced bacteria from seven families (pets included) and their homes over six weeks. They swabbed the surfaces of skin, hands, feet, noses, countertops, doorknobs, and nearly every surface with which the residents interacted in their abodes. Turns out, our bodies release bacteria in almost every encounter we have with our environment—when we shed skin, when we yawn, when we open the fridge door. And that germ-sharing happens rapidly. When three of the families in the study moved to a new house, it took less than 24 hours for their new places to look exactly like their old ones, at least when it came to their bacterial housemates. And that was true even when the new place was a hotel room.
“People get very fidgety and itchy about hotel rooms,” study author Jack Gilbert, a microbiologist at the U.S. Department of Energy’s Argonne National Laboratory, says — from his hotel room in South Korea. “But realistically, my hotel room right now looks like my microbiome. I’ve wiped out any of the previous occupants’ microflora in here—it’s 99.9% me.”
We don’t only share our bacteria with our houses, but also with each other. In the study, couples and their young children shared the most microbes with each other, thanks to regular physical contact. Hands were the most similar microbially, while noses retained an air of germy individuality since we pretty much keep them to ourselves (thank you, tissues!). The microbial constellations of families were so specific and unique that researchers were able to predict which family a given set of floor germs belonged to.
That’s fine when it comes to the more benign microbial hitchhikers, but what about the more scary ones that can cause disease? The researchers tracked a potentially antibiotic-resistant human pathogen from a kitchen countertop to the hands of family members, but no one got sick. “It’s likely that we all carry around nasty pathogens all the time in our body,” Gilbert says. “People aren’t getting ill because of them.” So our immune systems are able to ward off many of the nastier bugs most of the time — as long as we’re relatively healthy. Gilbert believes that it’s only when our microflora are compromised or unbalanced that the bad bugs get the chance to attack us.
Exposing your immune system to a wider array of the microbial universe is another way to bolster your defenses against them. And one way to do that is to get a pet. Dogs and cats track in the outside world, and that includes microbes. In the study, families with pets had more plant and soil bacteria in their homes — and that’s a good thing: a study earlier this summer found that infants who lived among pet dander had lower rates of allergies. “[Having a dog] rapidly supercharges the highways of microbial transmission in the house,” Gilbert says. (He is so convinced by the results, in fact, that he got a dog.)
The results are just the beginning of understanding how we interact with our environment, including with elements that we can’t even see. “There’s a continuum between you and your world, not a brick wall that ends at your skin,” says Gilbert. “We have to really embrace it in every aspect of our lives.”