Couples who live together share numerous things, such as a bedroom, bathroom, toiletries, and food. One thing they might not expect to share? Their microbiome! After analyzing skin microbiomes from couples who live together, microbial ecologists found that cohabiting partners can greatly influence the microbial communities on each other's skin. After all, sharing is caring. Right?
What is the Skin Microbiome?
The microbiome refers to a community of trillions of microorganisms that inhabit both the inner and outer surfaces of the human body. Microbial surveys show that bacteria, archaea, fungi, protozoans, and arthropods are present on the skin. This diversity manifests its differences in microbial composition not only from person to person but also between body parts. Most of these microorganisms are not dangerous. In fact, growing evidence suggests that they have many beneficial properties.
What’s Mine is Yours
Each individuals’ skin microbiome is unique to themselves. However, living with someone can alter this uniqueness.
One study analyzed microbial communities from 17 different skin sites of 10 sexually active partners and compared the microbes identified. They found that cohabitating can significantly influence the skin microbiome, but not so much that they have merged into identical microbiomes. In fact, computer algorithms relying on microbial data were able to accurately match couples with up to 86 percent accuracy based on their skin microbiome.
The body sites tested were the nostrils, armpits, navel, thighs, soles of feet, eyelids, nose, torso, back, and hands. Of these sites, the feet had the most diverse communities of microorganisms and were most similar between partners. In addition to the feet, the hands, back, torso, navel, and eyelids also had similar microbial communities between partners. Unlike the other body sites, the outer nose had the least similar microbiome shared among partners.
Other factors such as biological sex and body location may have more of an influence on the skin microbiome than from cohabitating partners. For example, microbial communities of the inner thigh were more similar among those of the same biological sex than between cohabitating couples. Computer algorithms could correctly identify the female sex with 100 percent accuracy by analyzing samples from the inner thigh alone. Swabs from other body parts did not yield the same perfect results but were identified 80 percent of the time.
How is the Skin Microbiome Exchanged?
Humans shed over one million biological particles per hour.[2,3] “Shedding” is a natural and normal human process in which dead skin cells slough off. This constant shedding can change the composition of surfaces and the immediate environment. This phenomenon is also referred to as a microbiome cloud. Basically, where you go, as you shed your dead skin cells, your microbiome cloud follows you.
When sharing a living environment, it can be expected to naturally pick up your partner’s microbiome, as well as share your own due to this constant shedding. This exchange can be caused by three primary mechanisms:
- Direct human contact.
- Airborne biological particle shedding though breathing, clothing, skin, and hair.
- Resuspension of indoor dust containing previously shed human skin and hair cells, as well as other bacterial-laden particles.
These mechanisms explain how and why partners who live together can be expected to have similar microbiomes. As previously mentioned, the microbiome of the feet, hands, back, torso, and eyelids in cohabitating couples are the most similar in comparison to the other body parts. It is thought that the transfer of these microscopic organisms occurs in these locations based on day to day living habits with a partner. For example, walking on the same floor barefoot, sharing the same bed and sheets, holding hands, and quite simply being in each other’s microbiome cloud.