A “bug atlas” of the human body has revealed where microbes are most likely to thrive - such as on the hands

A "bug atlas" of the human body has revealed where microbes are most likely to thrive.

Hotspot skin sites of bacterial diversity included the forearms, palms, index finger, the back of the knee and the sole of the foot.

The US study showed that humans carry their own personalised communities of bacteria around with them.

Unexpectedly wide variations in microbe populations were seen between different individuals.

Scientists focused on 27 sites of the human body in nine healthy volunteers. Each was sampled four times over a three month period, usually an hour or two after a shower.

The researchers, from the University of Colorado at Boulder, probed numerous niches where bugs were likely to be found, including ear canals, nostrils, the mouth, and the lower intestine. A total of 18 different skin sites were tested ranging from the forehead and armpits to forearms, palms, fingers, navels, the back of knees and the soles of feet.

Bacterial diversity was highest in the lower intestine and at certain skin sites. One type of bacteria dominated the head regions while another was most prevalent on the trunk and legs. The least variation both within individuals and between people was seen in the mouth cavity.

Study leader Dr Rob Knight said: "This is the most complete view we have yet of the microbial side of ourselves, one that our group and others will be adding to over the coming years. The goal is to find out what is normal for a healthy person which will provide a baseline for further studies to look at people with diseased states. One of the biggest surprises was how much variation there was from person to person in a healthy group of subjects."

The researchers speculated that drier areas of the skin such as the forearms might make more hospitable "landing pads" for bacteria. Details of the study were published in the journal Science.

An estimated 100 trillion bugs live on and within every human being. On the whole they are beneficial, contributing to the proper development of immune systems, efficient digestion and resistance to invading harmful bacteria.