Women's hands 'harbour more bugs'

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Women have a greater range of different types of bacteria on the palms

of their hands than men, US research suggests.

The study also found that human hands harbour far higher numbers of

bacteria species than previously thought.

Using powerful gene sequencing techniques, researchers found a typical

hand had roughly 150 different species of bacteria living on it.

The Proceedings of the National Academy of Sciences study found

bacteria types varied greatly between individuals.

The researchers, from the University of Colorado at Boulder, hope their

work will help scientists to establish a " healthy baseline " of bacteria

species on the human hand.

This could potentially help them to identify which species are linked

to specific diseases.

Lead researcher Dr Noah Fierer said: " 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. "

The study detected and identified more than 4,700 different bacteria

species across 102 human hands in the study.

However, only five species were shared among all 51 participants.

Even the right and left palms of the same individual shared an average

of only 17% of the same bacteria types.

Acidic skin

Dr Fierer said that the higher bacterial diversity on women's hands may

be due to the fact that men tend to have more acidic skin, which

provides a more harsh living environment for the microscopic bugs.

BACTERIA ON WOMEN'S HANDS

Enterobacteriales: 400% more abundant on women

Moraxellaceae: 180% more

Lactobacillaceae: 340% more

Pseudomonadaceae: 180% more

Alternatively, differences in sweat, oil gland or hormone production

may be key - or the fact that women and men tend to make different use

of cosmetics such as moisturisers.

Dr Fierer said the study also found hand washing had little impact on

the diversity of bacteria found on an individual's hands.

While some groups of bacteria were less abundant following hand

washing, others were more abundant.

However, the researchers said that washing with anti-bacterial

cleansers was still an effective way to minimise the risk of disease,

as it seemed particularly to target harmful bugs.

The diversity of bacteria types on the palm was three times higher than

that found on the forearm and elbow and appeared to outstrip that found

in the mouth and lower intestine.

Important role

Dr Fierer said: " We know that skin associated bacteria are likely to

have an important influence on skin health, a minority may act as

pathogens and many may actually have a beneficial effect, protecting us

from disease.

" However, we do not know how differences in bacterial communities may

impact skin health and we do not know if specific types of bacteria are

more beneficial than others.

" This is an active area of research but our results suggest that

answering these questions will be very difficult given that there is so

much background variability in bacterial communities between healthy

individuals. "

Dr Curtis, director of the Hygiene Centre at the London School

of Hygiene and Tropical Medicine, said science still had much to learn

about how bacteria interact with the human body.

She said: " Most are likely to be neutral, just living there without

doing any harm or good. "

But she added: " It is thought that having such flora on our hands is

probably beneficial, because the bacteria occupy niches which are then

unavailable to pathogens. "