Women have a greater variety of bacteria on their hands than men, according to a new study from the University of Colorado at Boulder. In addition, everyone has more varieties of bacteria than they think.
Scientists across the country are working on a program to map the genetic makeup of the germs  that share space in human bodies. Swabbing the palms of 51 college students was part of that program.

“The sheer number of bacteria species detected on the hands of the study participants was a big surprise, and so was the greater diversity of bacteria we found on the hands of women,” said Noah Fierer of University of Colorado’s department of ecology and evolutionary biology.

Researchers attributed the differences between men and women to be environmental and gender-based: men’s skin is more acidic and women’s hands have thinner skin, use more cosmetics and moisturizers and the differences between sweat and oil glands could be a factor.

But fear not: The vast majority of bacteria on the skin is harmless or helpful, the researchers said.

Here’s what they found:
* In tests of 102 hands of college students, researchers found 4,742 species of bacteria overall.
* Only 5 species were on every hand.
* The average hand harbored 150 varieties of bacteria.
* Right and left hands had a 17 percent difference in bacteria species.
* While researchers could count the species of bacteria, they couldn’t  count number.
The National Institutes of Health and the National Science Foundation paid for the study. Find it in the online edition of the Proceedings of the National Academy of Sciences.