Alcohol-based hand sanitizers are more effective than
antibacterial soaps, but don't give up on plain soap and water.
That our hands are crawling with germs is old, old news. Adults
have hectored children about the dangers of unwashed hands for
generations. Over a century ago, a few pioneering doctors
(Holmes, Semmelweis, Lister) figured out that physicians' hands
were infecting patients and making many people sick.
What is new, though, is the range of organisms you might find on
even a seemingly clean pair of hands.
It's pretty normal to have staph germs living on your skin (and
in your nose): About 25%–30% of us are "colonized" with no ill
effects — unless the bacteria get into a break in the skin. But a
new version is increasingly prevalent: methicillin-resistant
Staphylococcus aureus (MRSA), a bacterium that resists
not only methicillin but many other antibiotics. MRSA was once
almost exclusively found in hospitals. Now outbreaks are
occurring at schools, in jails, and among sports teams. Members
of the Boston Celtics pro basketball team were infected in the
fall of 2006
Clostridium difficile, a bacterium found in feces, is
another hospital germ that's flown the health care coop. Hands
are often the middleman in the fecal-oral transmission route:
C. difficile gets on people's hands when they come in
contact with a contaminated surface or object, and they
inadvertently infect themselves when their hands touch their
Our hands are much more hospitable to bacteria than to viruses,
but you'll find a few of the latter. Most flu is transmitted
through the air in virus-laden droplets propelled by coughs and
sneezes. But our hands can pick up those droplets from any number
of surfaces, so they're often an important link in the chain of
transmission. Hand washing is a standard item on flu-prevention
lists, and health officials are putting special emphasis on it
now because of the bird flu epidemic.
Americans say they wash their hands. Over 90% of those
questioned in a telephone survey said they washed up after using
a public bathroom. But when the American Society of Microbiology
and a trade association group observed people in public restrooms
(in stadiums, train stations, etc.), they found that only 75% of
men washed their hands. Women weren't perfect, but at 90%, did
better than the men. This Mars-Venus disparity extends to those
with medical degrees. In one study, female physicians washed
their hands 88% of the time after seeing a patient; their male
colleagues did so only 54% of the time.
Overkill overdoes it
There are those, both men and women, who overdo the hand washing.
Our hands weren't meant to be sterile objects. Having some
bacteria on the skin is perfectly natural, and "resident flora,"
as the experts call it, is probably healthful — unless you're a
surgeon about to put your hands inside someone's body. Frequent
hand washing, even with mild soap, can damage skin, worsening
cuts and causing cracks that can harbor even more bacteria. Dry,
damaged skin may also spread germs more easily because it flakes
off, taking bacteria with it.
How often should you wash your hands? There's no set frequency;
it really depends on your activities. Must-wash occasions include
after using the bathroom, before eating or preparing food, and
after being with someone who's ill, particularly if he or she has
a respiratory or gastrointestinal infection.
New products clamor for our attention, but plain old soap and
water is still a good way to clean your hands. In studies,
washing hands with soap and water for 15 seconds (about the time
it takes to sing one chorus of "Happy Birthday to You") reduces
bacterial counts by about 90%. When another 15 seconds is added,
bacterial counts drop by close to 99.9% (bacterial counts are
measured in logarithmic reductions). Few of us wash our hands
that long — 5 seconds is more like it. One reason you're supposed
to use cool or lukewarm water is to increase the chances you'll
wash them a little longer. Hot water is also more damaging to
Soap and water don't kill germs; they work by mechanically
removing them from your hands. Running water by itself does a
pretty good job of germ removal, but soap increases the overall
effectiveness by pulling unwanted material off the skin and into
the water. In fact, if your hands are visibly dirty or have food
on them, soap and water are more effective than the alcohol-based
"hand sanitizers" because the proteins and fats in food tend to
reduce alcohol's germ-killing power. This is one of the main
reasons soap and water is still favored in the food industry.
Even people who are conscientious about washing their hands make
the mistake of not drying them properly. Wet hands are more
likely to spread germs than dry ones. It takes about 20 seconds
to dry your hands well if you're using paper or cloth towels and
30–45 seconds under an air dryer.
By some accounts, almost half of the hand soaps on the market
have an antibacterial additive. Many brands are in liquid form,
so they're less messy than a traditional bar of soap, but you
can, of course, buy plain soap in liquid form, too.
The active ingredient in most antibacterial soaps is a chemical
called triclosan. Triclosan in the amounts used in soap doesn't
kill many bacteria (concentrations of 0.2% or less), but it keeps
the counts down partly because it has residual activity.
The big question has been whether widespread use of antibacterial
soaps will worsen the problem of antibiotic resistance. Doctors
have worried that bacteria exposed to low levels of triclosan
aren't killed outright so much as given an opportunity to mutate
so their offspring are more resistant to triclosan and,
ultimately, to antibiotics as well. In the lab, that's how it has
played out: Bacteria that become less susceptible to triclosan
show indications of developing "cross-resistance" to antibiotics.
But what happens outside the lab is less clear. In the biggest
study of its kind, researchers recruited about 240 households in
upper Manhattan to participate in a "real-world" hand washing
study. Half were randomized to use 0.2% triclosan soap; half, to
plain soap. After a year, the researchers tested the hands of the
primary caregivers in the households for antibiotic-resistant
bacteria. The result: no statistically significant difference
between antibacterial and plain-soap households. The researchers
offered several possible explanations for their findings
(resistance may not develop in a year; high antibiotic use may
make it difficult to detect small changes), so the case isn't
closed, but their findings do counter the lab research.
Even if antibiotic resistance weren't an issue, results from this
study (and others) make you wonder if the antibacterial soaps
available to consumers add much to hand hygiene. In the Manhattan
households, a year of washing with an antibacterial soap didn't
lower bacterial counts on hands any more than a year of washing
with plain soap. Nor did the antibacterial soap households
experience fewer cold-like symptoms. That's not surprising: Colds
are caused by viruses, not bacteria. Still, the finding is a
useful reminder that the antibacterial soaps aren't the
all-purpose germ fighters that many people expect them to be.
Four dos and don'ts
Don't scrub. Scrubbing can damage
skin, especially if you do it a lot. The resulting
cracks and small cuts give pathogens a place to grow.
Keep your fingernails short.
Bacteria like the area under our fingernails. Long
nails make it more difficult to keep those areas
Use hand lotions, especially during the
winter. Keeping the skin of your hands
intact is essential to good hand hygiene.
Don't be in such a hurry. It takes
about a minute to properly wash and dry your hands.
Rubbing it in
The hot new products in hand hygiene are alcohol-based rubs, sold
as "hand sanitizers." Purell is the most popular brand-name
product, but you'll pay considerably less if you buy a
store-brand version. The big advantage of the alcohol-based
cleansers is that you don't need water (you just rub the stuff on
your hands) or a towel, so they can be used anywhere, not just in
the bathroom. Politicians use them on the campaign trail (see
box), and we've spotted bottles on people's desks and in their
cars. Although many surgeons still scrub in the way seen on
television, some have switched to an alcohol-based foam,
transforming that iconic image of hand hygiene.
Can we shake on that?
Who touches more dirty hands than a politician on the
In his book, Sen. Barack Obama says President Bush is an
enthusiastic user of hand sanitizers. Obama describes a
brief conversation he had with the president during a
visit to the White House. "Good stuff, keeps you from
getting colds," Bush told the Illinois senator before
offering him a squirt, which the Democrat says he
accepted because he "did not want to appear unhygienic."
Perhaps this is one area of bipartisan agreement.
According to The New York Times, Obama now keeps
his own bottle of an alcohol-based cleanser in his travel
Alcohol's killing power comes from its ability to change the
shape of (denature) proteins crucial to the survival of bacteria
and viruses. In the United States, most of the alcohol-based hand
cleansers sold to consumers are 62% alcohol. By itself, alcohol
would completely dry out people's hands, so various skin
conditioners are added. Alcohol does a superb job of getting rid
of bacteria and even some viruses. In all but a few trials,
alcohol-based cleaners have reduced bacterial counts on hands
better than plain soap, several kinds of antibacterial soap, and
But alcohol doesn't kill everything: bacterial spores, some
protozoa, and certain "nonenveloped" viruses aren't affected.
That's why it shouldn't be the only cleaner available in
hospitals or other health care settings, according to Dr. Duncan
Macdonald, a surgeon in Glasgow, Scotland, who has studied hand
hygiene. Dr. Macdonald says hospitals where he has worked go back
to soap and water during "winter vomiting outbreaks" caused by
To be effective, the alcohol-based rubs need to come into contact
with all the surfaces of your hands — back, front, in between the
fingers, and so forth. For that reason, studies have shown that
using small amounts — 0.2 milliliters (ml) to 0.5 ml — is really
no better than washing with plain soap and water. Dr. Macdonald
reported study results in 2005 that showed coverage with an
alcohol-based gel improved considerably when he had hospital
staff members double the amount they used from 1.75 ml to 3.5 ml.
In another study, Dr. Macdonald found that coverage also improved
if staff members saw the areas they missed under an ultraviolet
light and were then shown the six hand washing steps designed to
maximize coverage, regardless of the type of cleanser (see
Six steps to super-clean hands
At the Health Letter, when we measured a squirt from a
bottle of Purell hand sanitizer, it was 0.5 ml at most, which
would suggest that a single squirt isn't much better than washing
hands the old-fashioned way. So keep in mind that the way we
actually use alcohol-based products may not be leaving our hands
quite as germ-free as we suppose. On the other hand (pun
intended), their convenience may mean people will clean their
hands more often, especially if they're on the go, so hand
hygiene might improve over all.
Dr. Macdonald sees no need to use alcohol rubs at home: "I use
regular soap and hot water and have no intention of throwing out
my pleasant-smelling lotions for alcohol rubs. Most of the germs
around the home have come from us and live with us in perfect
harmony." The exception, he adds, might be if you are caring for
someone who's at high risk for infection.