My mother always made us take our shoes off just inside the doors of our home. Did that make scientific sense back then or now? Although most of us would not track wet, sandy or muddy shoes into living quarters, many of us routinely make an entrance wearing shoes that are dry and free of visible debris. Mindful of the potential risks from exposure to the invisible microbes adhering to the bottom of their shoes, however, some people leave their footwear at the door. Of course, in some cultures, outdoor shoes are never worn indoors and alternative footwear such as slippers or slipper socks are provided at the entrance to the home.
An April, 2017 Wall Street Journal article concludes that taking your shoes off indoors is both “good manners” and “good hygiene,” but not critical in most cases. With 178+ reader comments posted to the article, it’s pretty clear there are many thoughts on the subject!
Shoe Soles: A Menagerie of Microbes
Studies show the soles of shoes transport a variety of microbes. University of Houston’s Dr. Kevin W. Garey, is quoted in the Wall Street Journal article as saying, “Shoes are a menagerie of microorganisms, sometimes carrying dangerous bacteria.” He implies, however, that unless residents suffer from an underlying condition that makes them susceptible to infection, or they are elderly or very young, they run little risk of getting sick from the microbes clinging to their shoes.
Dr. Garey and his colleagues conducted a study of the prevalence of the superbug bacterium, Clostridium difficile, or “C. diff” on the soles of shoes from the Houston area. The researchers found C. diff on over 25% of the roughly 2,500 shoes sampled. Austrian researchers found at least 40% of shoes sampled carried Listeria monocytogenes (usually transmitted through contaminated foods) and a German study found E. coli (normally found in the intestines of people and animals) on over 25% of boots worn on farms. Wiping your shoes or boots on a door mat may remove some of the debris that harbors microbial pathogens, but the action also likely leaves pathogens there for pickup by the next pair of shoes (or socks or bare feet) to traverse the mat.
Advice for Shoe Wearers
The researchers interviewed for the Wall Street Journal article agree that the risk from leaving your shoes on upon entering living quarters is normally “muted” and “not something to freak out about,” but a pretty good idea. That makes sense, but it also makes sense to scale your actions to the potential risk of exposure of residents in the home to pathogens. For example, if you are entering the home of someone in precarious health or a toddler who is in constant contact with the floor and carpets, stepping out of your shoes is prudent. Otherwise, leaving your shoes at the door is polite and hygienic, but not a “must,” unless required by your host. Overall, use your best judgment.
Bruce K. Bernard, Ph.D., is President of SRA Consulting, Inc., and Associate Editor of the International Journal of Toxicology. He lives in Cambridge, MD surrounded by nature (e.g., lots of deer [which eat his wife’s tenderly grown flowers and leave droppings everywhere]), and two corgis who, having a doggy door come and go as they please, leaving droppings wherever they want. Thus, he removes his shoes when entering ‘his wife’s home’ (and laughs each time at the memory of his mother yelling to the kids to ‘take your shoes off’)!