Walking hand-in-hand with the one you love? I’m sure everyone loves the feeling, but you might change your mind after reading this article. More exactly, you might be surprised to find out how many germs your hands harbor, especially women’s hands.

“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 lead researcher Noah Fierer, an assistant professor in Colorado’s department of ecology and evolutionary biology.

Are you still holding hands? Probably yes, but let’s go further and see what’s new.

Using powerful gene sequencing techniques, researchers found a typical hand had roughly 150 different species of bacteria living on it. Overall, more than 4,700 bacterial species were identified on all hands, only five of which were common among the palms of 51 undergraduate students who volunteered to be screened. Bacteria varied not only from one person to another but also between the right and the left hand of the same individual. To be more specific, the left and right hand of the same individual shared only about 17 percent of the same bacteria types, the researchers found.

On average, women had 50 percent more bacterial species on their hands than men. Moreover, women also may have more bacteria living under the surface of the skin where they are not accessible to washing, Knight added.

However, the researchers could not explain the phenomenon. They suggested though that the higher bacterial diversity on women’s hands may be due to the act that men tend to have more acidic skin, which provides a more harsh living environment for the microscopic bugs.

Moreover, differences in sweat and oil gland production between men and women, the frequency of moisturizer or cosmetics applications, skin thickness or hormone production might also contribute to the phenomenon.

Another surprising finding of the study was that the diversity of bacteria on individual hands was not significantly affected by regular hand washing.

“The vast majority of bacteria are non-pathogenic, and some bacteria even protect against the spread of pathogens. From a public health standpoint, regular hand washing has a very positive effect,” said University of Colorado biochemistry assistant professor Rob Knight, a co-author of the paper.

However, the researchers also noted the washing hands did not eliminate bacteria. Immediately after washing, a diverse community re-establishes itself within hours, but that does not mean that people should forget about washing hands. Fierer said that soap and water reduces abundance and has a large effect on pathogens.

The study, funded by the National Institutes of Health and the National Science Foundation, was published in the November 3 online edition of Proceedings of the National Academy of Sciences.