Armpits Are "Rain Forests" for Bacteria, Skin Map Shows

by Barbara McPherson | May 29, 2009 at 08:24 am

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A new study of the diversity of bacteria on healthy human skin has revealed a rich diversity of types(phyla) of bacteria. The areas with most bacteria are those that are damp or oily, like armpits and nose.
We know that a diverse group of bacteria are necessary for a healthy functioning gut. It now appears that the same principle applies to our skin. Apparently we have 20 different habitats on our bodies for bacteria, each with their own unique mix of organisms.

Most of our skin is like an arid desert, said study co-author Julia Segre, of the National Human Genome Research Institute in Bethesda, Maryland.

"But as you walk through this desert you encounter an oasis, which is the inside of your nose," she said. "You encounter a stream, which is a moist crease. [These] areas are like habitats rich in diversity."

And like the "friendly" bugs in the human digestive system, these native bacteria of the epidermis promote skin health and could even help scientists find new ways to treat skin diseases.

But by looking at the microbes' genes, Segre's team found at least 18 different phyla of bacteria dwelling in 20 different skin habitats. (In biology, a phylum is a group of animals that are similar enough that they likely share a common origin.)

What's more, these microbes are adapted to their habitats rather than to individual humans, Segre said.