from cdc.gov

Tuesday November 4, 2008 (foodconsumer.org) -- Women's hands are dirtier than men's in terms of the number of species of microbes harboring on the palms, according to a new study published online Nov 3 in this week's issue of the Proceedings of the National Academy of Sciences.

The study of 51 college students led by University of Colorado-Boulder Noah Fierer, Ph.D., showed that only five species were shared by all participants.

The right and left palms of the same individual shared only about 17 percent of the same bacteria types, and among all study subjects only 13 percent were shared with each other.

The study also found human hands harbored far more numbers of bacteria species than previously thought and women had a greater diversity of microorganisms on their hands than men.

Fierer and team found a typical hand harbored roughly 150 species of bacteria and in total 4,700 different bacteria species across 102 hands in the study were determined.

"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 Fierer.

The researchers speculated that men have less types of bacteria in their hands probably because men's skin is more acidic. Studies showed that microbes are less diverse in acidic environments.

The diversity of bacteria was fairly stable on individual hands and did not change much by regular hand-washing.

The authors said most of bacteria are non-pathogenic, meaning that they do no harm to humans.   Early studies found hand-washing with soap and water are effective at getting rid of germs on the hands.

The findings may help scientists to determine a healthy baseline of bacteria beyond which other bacteria could be associated with certain diseases, said Fierer.