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Hand Bacteria Percentage
Name: Heather
Status: Student
Age: 13
Location: N/A
Country: N/A
Date: 2002
Question:
How much (percentage) of bacteria
on the human body is on the hand? How much is killed when washing?
Replies:
I cannot give you an exact percentage, but the majority
of bacteria on or inside our body will be found in the
intestines. It will be less than 0.01% of those that
are present on our skin. Of those present on the skin,
I would say the proportion on the hands would be
roughly correlating to the proportion in skin surface.
Hands will be more exposed to bacteria than other skin
surfaces, as they touch more 'dirt', but the hand
palms have sweat glands to keep the skin surface
salty, and that is an unfriendly environment for
bacteria.
How many bacteria are killed by washing? That depends
on the time, and, to a lesser extend, to the soap you
use. Surgeons who have to clean their hands as good as
they can, use antibacterial soap and must wash for at
least 5 minutes. Our normal hand-wash routine usually
takes not even 1 minute. That is insufficient to kill
all bacteria, but do not worry: it is completely safe
to have bacteria on your hands.
Normal hygiene practice is completely sufficient under
normal conditions. As long as you are not a doctor
treating vulnerable patients, a normal hand wash with
normal (not even anti-bacterial) soap is all you need
to prevent trouble. Too much soap and hand washing can
lead to problems, like skin problems (and this can
lead to infections!) or psychological damage, as some
people become obsessed with bacteria. Remember, our
body is perfectly capable to cope with normal
bacterial load.
Trudy Wassenaar
Dear Heather,
A very similar question has recently been answered by Trudy Wassenaar and is
in the NEWTON Molecular Biology Archive:
http://www.newton.dep.anl.gov/askasci/mole00/mole00180.htm
The only point that question does not address is the actual "(percentage) of
bacteria on the human body on the hand". This would partially depend on the
hand to body surface area ratio, but the hand is often more readily exposed
to contamination, as well. So it is very likely that the hand has more
bacteria per unit area than the rest of the body, but I do not know that
anyone has actually done a quantitative analysis since this would require
somehow controlling for exposure, which would be difficult.
Jeff Buzby, Ph.D.
Children's Hospital of Orange County
NEWTON AAS
Division of Educational Programs
Argonne National Laboratory
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Update: June 2012
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