A typical hand has about 150 different species of bacteria living on it and bacterial colonies rapidly re-establish after hand washing.
That food for thought comes from a new University of Colorado at Boulder study that's found human hands are home to far higher numbers of bacteria species than previously believed and women tend to have a greater diversity of microbes on their hands than men.
The study, funded by the National Institutes of Health and the National Science Foundation discovered more than 4,700 different bacteria species on 102 human hands involved in the study.
While the diversity of bacteria wasn't significantly affected by washing, even with anti-bacterial soap, the research team says from a public health standpoint regular washing does have a very positive effect.
Washing causes some bacteria groups to become less abundant while others, some of which even protect against the spread of disease, can be more abundant.
Why women tend to have a larger collection of bacteria on their hands is a mystery.
Scientists speculate skin pH might play some role since men generally have more acidic skin and microbes tend to be less diverse in more acidic environments.
Differences in sweat and oil gland production, even hormone production could play a part.
It seems our left and right hands tend to dip into different cultures.
The researchers discovered the right and left palms of the same individual generally share only 17-percent of the same bacteria types.
The number of bacteria types found on the palm is typically three times higher than the richness found on the forearm and elbow.
There is one final "ugh" factor in the report. The amount and diversity of hand bacteria can even exceed the amount found in the lower intestine.
The researchers say the findings have implications for human health that health experts weren't even asking about six months ago.
Study details are published online in the Proceedings of the National Academy of Sciences.
(Copyright 2008 by Newsroom Solutions)