What Actually Lives in Your Belly Button?
A cotton swab, 67 species of bacteria, and the bizarre biodiversity hiding in the one place you probably never clean.
Written by Milieu Science Team
Reviewed by Andrea Echeverry, PhD
Push a cotton swab into your belly button and you will find, on average, 67 species of bacteria. In 2012, a team at North Carolina State University did exactly that, swabbing the navels of 60 volunteers as part of the Belly Button Biodiversity Project. What they found was astonishing: 2,368 bacterial species in total, more than 1,400 of which were new to science. One volunteer harbored bacteria previously found only in Japanese soil. Another hosted microbes typically seen in ice caps.
Your navel, it turns out, is a miniature rainforest.
So what's actually down there?
Most of what lives in your belly button is harmless. The usual suspects—Staphylococcus epidermidis, Corynebacterium species, a sprinkling of Cutibacterium acnes—are the same residents you'd find on your forearm or behind your ear. But the belly button offers something those flatter landscapes don't: a warm, moist, protected cave. It's a low-disturbance niche, rarely scrubbed or exposed to sunlight. That stability allows rare species to persist, slow-growing oddballs that wouldn't survive on your knuckles or forehead.
The depth and shape of your navel matters. Deeper "innies" host more diversity than shallow ones, likely because they trap more shed skin cells, sweat, and sebum—the substrates bacteria feed on. If you never clean it, you're basically running a time capsule.
The weird outliers
Some of the findings defied easy explanation. One participant's navel harbored Marimonas, a bacterium typically found in the ocean. He hadn't been swimming in years. Another hosted two species of extremophile archaea, microbes more commonly associated with hydrothermal vents. The researchers speculated these might be relics from previous environments—showers, swimming pools, a childhood trip to the coast—clinging on in a stable microhabitat long after the original exposure.
The belly button also seems to act as a biodiversity reservoir. Because it's left alone, it may preserve microbial lineages that disappear from more frequently washed or exposed skin sites. (For a sense of how variable microbial communities are across the body, see our overview of skin bacteria.)
How personal is your navel ecosystem?
Very. The North Carolina team found that no two belly buttons shared the same microbial community. Even among people living in the same household, navel microbiomes were as distinct as fingerprints—sometimes more so. The researchers could identify individuals based solely on the species composition inside their navels.
This isn't just taxonomic trivia. It suggests that even a small, sheltered patch of skin develops a profoundly personalized ecosystem shaped by genetics, immune function, hygiene habits, clothing, and past exposures. Your belly button is a biography written in bacteria.
Why this matters for your skin
If a tiny, neglected divot can harbor 67 species on average, imagine the complexity living across your entire body. Understanding that diversity—and how easily it's disrupted by over-washing, harsh products, or environmental shifts—helps explain why identical routines don't work for everyone. Your skin isn't a blank slate; it's a populated landscape, and what lives there shapes how it behaves.
References
- Hulcr J, Latimer AM, Henley JB, et al. A jungle in there: bacteria in belly buttons are highly diverse, but predictable. PLoS One. 2012.
- Grice EA, Segre JA. The skin microbiome. Nat Rev Microbiol. 2011.
- Byrd AL, Belkaid Y, Segre JA. The human skin microbiome. Nat Rev Microbiol. 2018.
- Oh J, Byrd AL, Park M, et al. Temporal stability of the human skin microbiome. Cell. 2016.
Put this into practice
Your skin is its own ecosystem. The fastest way to see what's actually living on yours — and what your routine should look like — is the Superbiome microbiome test.
