Why does every patch of your skin have its own microbes?
Your armpit, your forearm and your belly button are different habitats, and one volunteer who claimed not to have bathed for years had archaea in their navel.
▶ Start the storyYour skin is not one habitat but many, and each patch has its own microbes. Human skin carries around 1,000 species of bacteria from nineteen , most of them in the top layers of the and in the upper parts of hair follicles. Scientists split the skin into three main ecological areas: oily (), moist and dry. Propionibacteria and Staphylococci dominate the oily areas, while Corynebacteria together with Staphylococci dominate the moist places, like armpits. The microbes you find depend on what the patch offers, such as oil or moisture.
The community is also personal. The spaces between fingers and toes, the armpits and the navel area show the least similarity between people, while the spots beside the nostril, inside the nostril and on the back look much more alike from one person to the next.
Least alike
- Between the fingers
- Between the toes
- Armpits
- The navel stump area
Most alike
- Beside the nostril
- Inside the nostril
- On the back
Most of them behave as neighbours rather than invaders. Skin bacteria can help by preventing pathogens from settling, competing for nutrients, secreting chemicals against them or stimulating the skin's immune system. They also have a part in body odour: sweat itself is odourless, but bacteria consume it and make by-products that humans may find putrid.
The skin is a firm landlord too. Its surface layers are naturally acidic, partly from lactic acid in sweat and from the skin bacteria themselves.
It is not a simple friendship, though. The same microbes can be commensal, or pathogenic, often all three, depending on the strength of the person's immune system. So the skin is best seen as an ecosystem kept in balance, not a battlefield and not a sterile surface.
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Recap
Your skin is a patchwork of habitats, and each patch (oily, moist, dry) hosts a different set of mostly harmless microbes.
💡 A trick to remember it · Skin is a map with three weather zones: oily, damp and dry, each with its own tiny residents.
Surprising fact · Two Staphylococcus species once thought to dominate skin turn out, by gene reading, to make up only 5% of skin bacteria.
Connects to
- 🦠 Do the microbes on your body really outnumber your own cells ten to one?
- 🧬 How do scientists read a whole microbial community from one gene?
- 🦷 Is the plaque on your teeth a tiny city of microbes?
- 👶 Where do a baby's first microbes come from?
- 🪨 How did scientists discover that lichens are secretly two organisms?
- Bacteria
Sources (1)
No source, no claim. Every fact in this lesson (16 claims) cites at least one of these.