A new study shows that women tend to have a greater variety of bacteria on their hands than men: on average, 50% more bacterial species than men have. And both men and women tend to have many more types of bacteria on their hands than previously thought.

The study, published in this week's issue of the Proceedings of the National Academy of Sciences, found more than 4,700 different bacteria species – most of which are harmless to people – on the palms of 51 college student participants. A typical student’s hand had around 150 different species of bacteria living on it. Only five species were found on the hands of all 51 participants. Interestingly, the right and left hand of an individual shared an average of only 17% of the same bacteria types.

Researchers aren’t sure why women seem to carry a greater variety of bacteria than men, but they speculate that it might have something to do with differences in the acidity of the skin between men and women. Men generally have more acidic skin than women, which may provide a less hospitable environment for some bacteria. Other possible explanations include differences between men and women in sweat and oil gland production, differing use of moisturizer or cosmetics, variations in skin thickness, or hormonal effects.

The study also showed the diversity of bacteria on individual hands was not significantly affected by regular hand washing. However, the study did not examine total numbers of bacteria, only the number of different bacterial species present.

To minimize risk your risk of disease, the researchers still recommend washing your hands regularly with antibacterial soap, as these cleansers seem to preferentially target potentially harmful bacterial species. If you have further questions about bacterial infections, ask the experts at Healia Health Communities.

_{Photo: Janice Haney Carr, CDC}