Today.Az » Weird / Interesting » What lives under your fingernails?
23 June 2016 [17:18] - Today.Az
By Jason G Goldman
Washing your hands is the first defence against all kinds of
nasty bacteria. But do you wash under your fingernails? Maybe you should…
You probably know that handwashing is among the best means
of preventing the spread of germs. In many places, public health laws are in
place to ensure that those in the food service industry keep their hands clean.
On the other hand, no amount of scrubbing can ever rid the hand of all its
The impossibility of sterilisation is why doctors and nurses
so often wear gloves while interacting with patients. Indeed, nearly a hundred
years ago, physicians began to realise that bacteria would always show up in
tests even after multiple re-washings. But it wasn’t until the early 1970s that
researchers began to identify the reason that hand-dwelling bacteria was so
It turned out that covering the fingertips could keep hands
cleaner longer. Though it’s not the fingertips which are so full of bacteria,
but the fingernails. These thin keratin shields, made of the same stuff as
rhino or impala horns, harbour a bacterial menagerie.
It wasn’t until the late 1980s that scientists began to poke
around under our fingernails to see who, exactly, lives there. In one 1988
study, a trio of researchers from the University of Pennsylvania’s
Department of Dermatology swabbed the hands of 26 adult volunteers, all
employees of the university’s medical school who did not interact with
They found that the space under the fingernails, also called
the subungual region, was “an important site” for harbouring bacteria. Other
parts of the volunteers’ hands were home to hundreds to thousands of bacteria,
while the subungual areas yielded hundreds of thousands of bacteria per
fingertip. The fingernails harboured the same types of bacteria as the rest of
the hand, just a lot more of them.
The researchers reasoned that could be because the space
between the skin and nail creates a perfect environment for the growth and
proliferation of these minute lifeforms, thanks to both the physical protection
provided by the nail and all that moisture. The prior findings that persistent
scrubbing doesn’t sterilise the hand, combined with the finding from their
study “that there are significant numbers of bacteria in the subungual
compartment suggest[s] that this hand region may be relatively inaccessible to
antimicrobial agents during normal hand-washing procedures,” they wrote.
Think about it: the space under your fingernails is
completely impervious to the best, and simplest, means we have of preventing
the spread of diseases.
Indeed, a small but thriving area of research continues to
probe the very nature of the microbial life living on the fingernails of
nurses. And not just natural nails, but also artificial ones, or ones covered
In 1989, just one year following the University of Pennsylvania
study, a group of nurses wrote, “although unanswered questions
concerning the safety and practicality of artificial nails remain, many health
care workers have succumbed to fashion trends and are now wearing artificial
The researchers wanted to see whether 56 nurses with artificial
nails, which tend to be longer than natural nails and are almost always covered
in nail polish, had more bacteria on their fingertips than 56 nurses with
natural nails. They also wanted to see whether handwashing was more or less
effective for those with artificial nails.
They discovered that nurses with artificial nails had more
bacteria on their fingertips than did those with natural nails, both before and after
handwashing. That’s not to say that they were actually transferring more
bacteria to their patients, necessarily, only that the bacteria living on their
fingertips were more numerous. Still, the assumption is that more bacteria at
least increases the potential for pathogen transmission.
Similar studies published in 2000and 2002 yielded similar results. But by
then, nursing researchers had evidence that artificial nails were also
associated with poor handwashing practices, which only served to compound the
problem. And artificial nails, they realized, were also more likely to tear
Painted, natural nails, on the other hand, tell a different
story. The fear with polish is that tiny chips or cracks in the paint could
harbour bacteria. In 1993, nurses from Johns
looked at the fingernails of 26 adult women who were employed by the hospital,
but not involved in patient care. All had short fingernails, and all were
assessed both before and four days after nail polish was applied.
Nail polish on natural nails did not seem to affect the
richness of fingertip bacterial micro-biodiversity in the same way as polish on
artificial ones, however. “Keeping nails short and clean, therefore, is
probably more important than whether or not nail polish is worn,” the
researchers concluded. Another study conducted the
following year reached a similar conclusion. While polished
nails more than four days old had more bacteria, freshly polished nails were
Some two to three million people die each year from
diarrhoea; it’s thought that handwashing with soap
could save perhaps a million of them. And it probably can. But in addition to
handwashing, the best course of action seems clear: pay special attention to
the subungual compartment beneath your fingernails when washing your hands, and
for the least bacterially hospitable fingertips, keep them short and clean.
All of which should give you pause before biting your nails.