Love, Roommates, and the Microbiome: How Moving in Together Changes More Than Your Closet Space

• Cohabiting partners tend to have more similar gut microbiomes than even siblings—suggesting that a shared environment can shape the microbiome more than genetics.
• Microbial sharing happens through more than food—daily routines, close contact, and even pets contribute to microbiome convergence.
• Your microbiome may quietly reflect your relationships, evolving alongside the people (and pets) you share your life with.

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Research shows your microbiome syncs with the people—and pets—you live with. Here's what that means for couples, roommates, and newlyweds.

Spring and summer are seasons of new beginnings. Wedding bells ring, leases turn over, and couples move in together. But alongside the housewarming gifts and closet-sharing negotiations, something unexpected happens: your microbiome—especially the one in your gut—starts to reflect your new living situation.

And not just from the stress of moving or the celebratory cake. Science shows that living together—especially romantically—shapes your microbiome, often making it more similar to the person (or pet) you’re living with. It’s a quiet, invisible kind of intimacy.

Cohabiting? Your microbes might be too

While there’s still a lot to uncover about the various microbiomes in and on our bodies, one thing we’re learning is surprisingly intuitive: people who live together—especially romantic partners—tend to have more similar microbiomes than people who don’t. It’s probably not something you’ve thought about before, but once you hear it, it clicks. Let’s take a look at what the research shows.

Several research groups have found that people who cohabit, particularly spouses, experience microbiome convergence, with microbial communities that are noticeably more similar than those of unrelated individuals living apart—even after controlling for key factors like age, diet, and overall health status. In fact, in one study of older adults, researchers found that cohabiting partners had gut microbiomes more similar to each other than to their own siblings—suggesting that the impact of sharing a home might be stronger than genetics over time (Dill-McFarland et al., 2019).

So, what’s driving that microbial convergence?

It likely comes down to the many ways we share space and life with the people we live with. Shared meals are a big one—similar diets shape similar microbial communities. But it’s more than just food. Shared environments (think kitchen counters, bathrooms, air), shared routines (like sleeping and waking at the same time), and physical touch all open doors for microbial exchange and transmission. And yes, physical intimacy matters. In fact, one study was able to correctly identify study participants' partners 86% of the time based on their skin microbiome alone (Ross et al, 2017).

Skin-to-skin contact and even kissing have been shown to transfer not just affection, but microbes. A 2014 study found that couples who kissed frequently had more similar oral microbiota than couples who didn’t, and that just one kiss could transfer tens of millions of bacteria (Kort et al., 2014). While that study focused on the mouth, it speaks to how our microbes travel between bodies through close contact.

Over time, this kind of microbial sharing starts to shape a shared internal environment—one that mirrors the life you’re building together externally. Your microbiomes quietly evolve into something a little more “us” than “me.”

Pets: the microbial middlemen

And it’s not just the humans you live with who shape your microbiome—your pets play a role, too. Studies have shown that homes with dogs and cats tend to foster distinct microbial environments, influencing the gut microbiota and skin microbiomes of the people who live there (Abdolghanizadeh et al., 2024).

In a landmark 2013 study, researchers swabbed households and found that people who lived with dogs had microbial communities that were not only more similar to each other but also more diverse overall. Dogs were like microbial bridges—trafficking skin, environmental, and gut bacteria between individuals and different areas of the home (Song et al., 2013). One 2017 study found that infants growing up in homes with pets—especially dogs—developed more diverse gut microbiomes and had a reduced risk of allergic diseases later in life (Tun et al., 2017). While that research focused on babies, the broader takeaway is clear: pets, by their very nature, reshuffle the microbial deck. They bring in outdoor microbes, interact closely with us, and essentially act as microbial messengers between environments.

Cats can also shape the microbial landscape, though their influence seems to be a bit more subtle—particularly on the gut microbiome, where their behaviors and contact with humans may still make a noticeable impact (Du et al., 2021).

So whether they’re curled up in your lap or tracking dirt through the house, pets aren’t just keeping you company—they might be shaping your microbiome too.

Microbial merging: why it matters

There’s something deeply poetic about the idea that your microbiome reflects your relationships. It adds a new layer of meaning to the act of moving in together, or saying “I do.”

You’re not just sharing space or lives—you’re sharing ecosystems.

It also raises questions for future research: could changes in your microbiome affect your mood, health, or even relationship dynamics over time? While we don’t have definitive answers yet, early research shows links between the gut microbiome and emotional well-being, immune function, and maybe even social behavior (Xiong et al., 2023; Zheng et al., 2020; Agranyoni et al., 2021).

Making moves this season

So as we head into wedding season and summer moving season—times when people start cohabiting in earnest—it’s worth taking a moment to appreciate the microbial remixing happening behind the scenes.

Whether you’re combining households, adopting a new pet, or just sharing a summer sublet with friends, know this: your microbiome is along for the ride. And chances are, it’s making new friends, too.