I was eating my lunch when I read this article, published today, about the diversity and sheer number of bacteria found on hands. A study from the University of Colorado showed that not only were bacterial counts 100 times greater than previously thought,  but that the diversity of bacteria was also far greater – even after handwashing. The study also reported that women have higher counts than men. With that news, I put down my sandwich and washed my hands – again.

Funded by the National Institutes of Health and the National Science Foundation the study found that on average, each hand had over 150 different types of bacteria with more than 4,700 different species identified on the hands of 51 undergraduate students who were involved in the study. Only about 5 of them were common among all the students sampled and there were different kinds of bacteria found between the right and left hands.

As a health care provider, what really surprised me was that hand washing did not seem to affect the diversity of bacteria that were found. Handwashing decreased the overall count of bacteria but didn’t seem to affect the diversity of bacteria that was found.

What does all this mean? Like any good study, it raises more questions than it answers. Why do women have more bacterial diversity than men? What is the role of hormones, pH, topical creams/lotions, sweat glands etc on the diversity of bacteria found between genders? Why does the bacterial type differ depending on dominant vs non-dominat hand? What protective benefits do we get from certain bacteria? What is the safe level of bacteria? Can we predict the health of an individual given the types and counts of bacteria found on the hands?

I’m pretty compulsive about washing my hands especially since our microbiology teacher had us swab anything we wanted and our class swabbed doorknobs, faucets, handles that flush toilets – you get the idea. But after reading this article, I found myself paying even more attention to the palms of my hands. If you’re interested in reading more about this study, click on this link.