Couples share 30% of their gut bacteria. Here’s how that may affect health

Conor Meehan, Nottingham Trent University and Janelle Mwerinde, Nottingham Trent University

When living with a partner, you might be sharing more than just the same home, lifestyle and interests. You might also share various microscopic organisms residing on and in you.

This community of microorganisms, which consists of mainly bacteria, viruses and fungi, is known collectively as the human microbiome. The various microbiomes found throughout the body all play an important role in health.

From birth, the human microbiome is shaped by our interactions with our mother, who introduces diverse microorganisms that build our immune and digestive systems. As we get older, social interactions with our close community continue influencing this delicate ecosystem.

The people we live with have huge influence on what microbes we have in our microbiome. In fact, it’s thought that partners share around 30% of their resident microbes in the gut alone.

But it isn’t just the microbes in your gut that may be similar to your partner. The microbes in many other parts of the body may also be shared with your loved one – and this could potentially affect your health.

Gut microbiome

Diet and lifestyle are thought to have the greatest influence on the gut microbiome’s make-up. But studies on couples have found that living with your partner can also influence the microbiome.

Couples living together may share 13% to 30% of their gut bacteria. This was true even when diet (which many couples share) was factored out. Research also shows that couples who live together have greater microbial diversity compared to people who live alone.

This is good news for couples who co-habitate, as a more diverse gut microbiome is correlated with lower risk of irritable bowel syndrome, cardiovascular diseases and potentially high blood sugar.

But it might not all be good news. Research shows that some of the bacterial species couples share can have varying effects on health.

Take the bacteria from the Ruminococcus family. While some species of Ruminoccocus benefit health, others have been linked to negative health outcomes, including diabetes and irritable bowel syndrome.

So these bacteria may not always offer the same benefits in different demographics. This highlights the complexity of resident gut bacteria and their health impacts.

Oral microbiome

Sharing an oral microbiome with our partners might seem obvious considering we regularly exchange saliva when we kiss. A ten-second kiss alone can exchange up to 80 million bacteria. The more kisses a couple shares, the more shared salivary bacteria they will have.

Although most of these bacteria will quickly pass through our mouth and into our gut when we swallow saliva, research show that couples actually share many of the same longer-term tongue microbes that form the foundation of the oral microbiome. Research even suggests that 38% of the oral microbiome is shared in couples living together – compared to only 3% in couples who don’t live together.

Sharing this proportion of your oral microbiome could have many potential health effects.

A healthy oral microbiome is important for protecting against tooth decay and it has anti-inflammatory properties. Some researchers also suggest the oral microbiome’s health effects may extend as far as the gut and nervous system.

But some of the bacteria that couples tend to share may also have potentially harmful health effects.

Couples are more likely to have similar numbers of the bacteria Neisseria in their gut compared to single people. Neisseria can reside in the mouth for long periods of without causing disease.

Some Neisseria bacteria can be harmful and may cause meningitis. Yet some Neisseria bacteria actually fight against these meningitis-causing species, stopping them from overgrowing and causing harm.

So while you may want to avoid kissing someone when they’re poorly for obvious reasons, it turns out that a kiss even when you’re healthy can transfer all sorts of bacteria between the two of you.

More research is needed to really understand what overall effect sharing these bacteria with your partner has on health.

Skin microbiome

The skin microbiome is the most unique and personalised microbiome, tailored to each person. It’s even sometimes referred to as our microbial fingerprint.

Being the most exposed microbiome, the skin microbiome has evolved to be adaptable to external factors such as the climate and cosmetic products. No matter what, these bacteria work hard to remain at an equilibrium.

Close contact with our partners – and even pets – has a huge influence on what bacteria live on our skin. After comparing the gut and oral microbiome, researchers found the skin microbiome to be the most similar among couples.

It isn’t just the bacteria on your arms or hands that are shared, either. Research shows that couples shared 35% of the bacteria living on their feet, and around 17.5% of the bacteria on their eyelids.

You may not even need to touch your partner to have the same skin bacteria as them. Factors such as sleeping in the same bed and walking on similar surfaces are thought to explain why such a large proportion of our skin microbiome is similar.

This is because humans naturally shed bacteria in a similar way as dogs shed fur. We leave traces of our bacteria on everything we touch – and we also easily pick up bacteria from our environments.

The shared effect of living together on the skin microbiome is so great that researchers were able to use computer models to accurately predict 86% of cohabiting couples based off of their individual bacterial samples alone.

But while it’s clear that couples share much of the same skin microbiome, the health effect that this has is not currently known.

While sharing bacteria with your partner may sound alarming, there’s often no cause for concern. Bacteria teach our bodies how to fight infections, they help us digest foods and even produce key nutrients. The bacteria we share with our partners are often harmless and sometimes benefit our health rather than hindering it.

Conor Meehan, Associate Professor of Microbial Bioinformatics, Nottingham Trent University and Janelle Mwerinde, PhD Candidate, Skin Microbiology, Nottingham Trent University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Read More........→March 20, 2026

Mom and Baby Beat 1-in-a-Million Odds to Survive the ‘Rarest of Pregnancies’

This photo provided by the family shows, from left, Kaila, Suze, Ryu and Andrew Lopez at Cedars-Sinai hospital in Los Angeles in August 2025 – family photo

A Los Angeles woman recently celebrated the first Christmas with her baby boy, Ryu, born to truly remarkable circumstances.

Ryu developed outside his mother’s womb, and remained hidden for months behind an ovarian cyst that grew to be the size of a basketball. It was so unbelievable, the surgical/OBGYN team that delivered Ryu documented it for a case study in a medical journal.

The manner in which Ryu came into being represents a circumstance that’s “far, far less than 1 in a million,” said Dr. John Ozimek, medical director of labor and delivery at Cedars-Sinai in Los Angeles, where Ryu was born. “I mean, this is really insane.”

Now 41, Suze Lopez has always had an irregular cycle, so missed periods—even consecutive ones—are a normal occurrence. It was almost 20 years ago that she was diagnoses with a pair of ovarian cysts, one of which was removed immediately, and one of which was not.

So in early 2025 when Lopez noted her abdomen swelling, her first thought was the cyst. She never felt kicking, and never had morning sickness—and indeed her instinct was at least partly correct.

The pressure and pain in her abdomen grew as days passed, and she was certain that, even if it risked her ability to conceive again, it was time to remove the other cyst which unbeknownst to her had grown to weigh a mind-boggling 22 pounds.

She needed a CT scan to prepare for surgery, which required a pregnancy test for the radiation, and to her utter surprise the test came back positive. Lopez was delighted, but the pain and discomfort grew and soon she had to be hospitalized at Cedars-Sinai where her medical team found a near fully-developed fetus in an amniotic sack lodged against her pelvis.

The term for where the fetus develops is “implants” and the term for a fetus that implants outside of the womb is an “ectopic pregnancy.” Almost all of these go on to rupture and hemorrhage. As such, fetal mortality can be as high as 90% in such cases and birth defects are seen in about 1 in 5 surviving babies, SF Gate reports.

However, because fetal Ryu implanted against the pelvic wall and not against the liver, it was far more manageable, and the reason why Lopez didn’t have more pain earlier.

Lopez and her boy beat the odds, despite a mammoth surgical procedure that both delivered Ryu at 8 pounds and removed the ovarian cyst—together weighing as much as an adult bobcat. During the procedure, Lopez lost half her blood, and had to be continually given transfusions.

“The whole time, I might have seemed calm on the outside, but I was doing nothing but praying on the inside,” Andrew Lopez, Suze’s husband, told SF Gate. “It was just something that scared me half to death, knowing that at any point I could lose my wife or my child.”Instead, they both survived without any maleffects. Ryu “completes” their family, said his mother, and recently celebrated his first Christmas alongside his older sister Kaila. Mom and Baby Beat 1-in-a-Million Odds to Survive the ‘Rarest of Pregnancies

Read More........→January 10, 2026