Should You Wash Your Hands?

  • By Anna Rothschild
  • Posted 05.11.17
  • NOVA

What do we really mean when we say that we’re clean? Gross Science explores hand hygiene, with some help from the show Clean My Space.

Running Time: 04:40


Should You Wash Your Hands?

Published May 11, 2017

For decades, we’ve assumed that a particular method of hand washing, or type of soap, is effective if it does a thorough job of removing microbes from your skin. But some scientists now think that we need to redefine hygiene.

So today, along with my buddy Melissa over at Clean My Space, I’m exploring what we mean when we say that we’re clean—and looking at just how important things like hand washing really are.

I’m Anna and this is Gross Science.

So, why would we need to rethink hygiene? Well, recently, scientists from the University of Oregon took a survey of studies focused on hand hygiene. For example, they looked at studies that weighed whether electric hand dryers are as good as paper towels.

Some studies supported electric dryer use, since they dry hands really well, and wet hands can transmit microbes more easily. Others found that electric dryers can blow microbes from our hands far across a room.

What none of the studies did was evaluate the health outcomes of people who used paper towels or hand dryers. Each study measured the presence or absence of bacteria, but they didn’t actually examine whether the microbes were harmful or not. So, the scientists proposed a new understanding of hygiene, which they defined (and I’m paraphrasing here) as actions that reduce the incidence of disease.

Now, you might be saying, “Isn’t that basically the same thing? Don’t microbes cause disease?” Well, not always. You see, we have millions of microbes living on our skin all the time, and most of them are probably good for us.

Take the bacterium P. acnes. While some strains of the bacterium can cause pimples, other strains produce antimicrobial agents that can kill certain disease-causing bacteria. And other types of healthy skin bacteria may help “train” our immune system, making it better able to fight infections in the future.

In fact, many scientists now think that conditions like asthma and allergies may be more common today because as kids we aren’t exposed to as many microbes, thanks to running water and other modern conveniences. And those microbes may be required to toughen up our immune systems.

Scientists first branded this idea the “Hygiene Hypothesis.” But more recently, some researchers have tried to refine or replace the idea, because the name may be a bit of a misnomer. It sort of implies that we should just stop cleaning our houses and washing our hands, opening ourselves up to lots of diseases. But some studies have shown that illnesses, like measles and the common cold, really don’t do much to improve our overall immune health or prevent us from getting allergies.

Instead, relatively harmless microbes that were super common in the natural environment may have played a big role in our health. This is what’s called the “Old Friends Mechanism.” These microbes were present all the time in our early evolution, so rather than fight them, they may have become parts of our immune system—constantly prodding it and teaching it what to attack and what not to. But, as we’ve moved into cities, changed our diets, and used tons of antibiotics, we’ve lost many of these old friends, and possibly opened ourselves up to less friendly microbes.

So basically, personal hygiene and house hygiene are still important for staying healthy. But some scientists now suggest that we should practice what’s called “targeted hygiene,” where we focus most of our attention on the biggest risk factors for disease. Hands, for example, are one of those targets. We’re constantly using them to interact with people, and animals, and the environment, so there are lots of opportunities for them to pick up germs. That’s why doctors recommend hand washing as a way to prevent the spread of illness.

There’s still more to learn about which microbes may be good, and which we want to get rid of. But for a fun explanation of how the CDC currently recommends that we wash our hands to stay healthy, go check out this video from Melissa over at Clean My Space.

Listen, anything we can do to prevent illness is great. But let’s not vilify ALL OF our microbial friends in the process—many of them are here to help. So, go out there and get a little dirty. You can always wash your hands when you get home.




Many thanks to Google’s Making & Science team for making this collaboration possible #sciencegoals
Host, Writer, Producer, Editor
Anna Rothschild
Illustrator, Animator
Jason Drakeford
Camera, Sound
Natasha Ishak
Rolling Underground
Music provided by APM
Many thanks to Dr. Roo Vandegrift


Original Footage
©WGBH Educational Foundation 2017
Hand Dryer
man with dirty hands
Shutterstock/Kim Reinick


(used with permission from author)
Squeak Pack/squeak_10
Running Water Bubbles 02
Hand dryer 9 hand movement
Marker writing on paper
Pencil Check Mark 2
Produced by WGBH for PBS Digital Studios


man with dirty hands
Shutterstock/Kim Reinick


Want More Info?

The concept of hygiene and the human microbiome:

Time to abandon the hygiene hypothesis: New perspectives on allergic disease, the human microbiome, infectious disease prevention and the role of targeted hygiene:

The Scientist: Microbes of the Skin:

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