How many times have you opened the door after being outside and walked through your house with your shoes on? Hundreds of times? Thousands? If so, here are some very good reasons you might want to take off your shoes.
Some bacteria are good for us, some harmful. A study conducted at the University of Arizona examined germs on shoes and found an average of 421,000 bacteria on the outside of shoes, with nine different strains of bacteria. Some of the harmful strains found on shoes included Escherichia coli, otherwise known as E coli, which can give you intestinal infections, diarrhea and in rare cases, meningitis; Klebsiella pneumoniae, which can cause urinary tract infections; and Serratia ficaria, which can cause respiratory infections. Yuck.
How do the bacteria get there? “We walk through things like bird droppings, dog waste and germs on public restroom floors, all of which are sources for E coli,” says Kelly Reynolds, Ph.D., a microbiologist and professor at University of Arizona. “The unique thing about the shoe environment is that other things you walk on like leaves and debris, can serve as food for the bacteria and help them grow.” That means potentially harmful bacteria can survive on your shoes for days or even weeks, Dr. Reynolds says. And that bacteria can be tracked onto your floors and carpets. It’s even grosser if you think about resting your shoes on a piece of furniture, or on your bed.
Another potential concern: toxins. A study by the Battelle Memorial institute, a nonprofit research group found that toxins from treating your lawn can easily be tracked into the house, and a study from Baylor University found that people who live near asphalt roads sealed with coal tar have an increased risk of cancer from toxins. The toxins, they found, settled inside the house as dust particles. Those particles can be brought in on your shoes.
“Think about rain water in the street,” says Dr. Reynolds. It can have gasoline in it and chemicals, and those get on your shoes and can be brought into your home.” But, she cautions, the exposure to toxins would be long-term, and you would most likely have to be exposed many times over the course of your life in order to get sick.
“Dirt isn’t harmful on its own,” says Dr. Reynolds, but you probably want to keep it at a minimum, especially if you have toddler grandchildren who play on the floor. “Kids often put their hands in their mouths, or have toys on the floor and put them in their mouths,” she says. One more plus to keeping your shoes at the door: It can cut down on how often you have to clean.