The final word on whether dragging in all that bacteria on your shoes will actually make you sick.
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You've always been a bit of a germaphobe. Your hermetically sealed home is a wonderland of disinfectants, antibacterial soaps and air purifiers. Say you invite a couple other friends over for a book club meeting and one of them strolls into your immaculate home wearing their nearly new Reebok Classics. She heads to the kitchen to assess the wine situation and you unleash a bloodcurdling scream: "TAKE OFF YOUR SHOES!"
Before she even has a chance to reply, you launch into a Streep-worthy monologue about how her footwear is swarming with E. coli, staph, C. diff, toxins, germs, viruses and all other manner of filth. Your friend awkwardly takes them off to reveal mismatched socks and slinks back to the living room in shame, where your fellow literati are quickly baring their feet to avoid a scolding.
But do shoes really carry that much bacteria?
Yes. Your shoes are covered in bacteria, viruses, germs and parasites. But also, it doesn’t matter. Unless you live in a sterile laboratory, the rest of your home is too – and so are you.
In 2016, a study by researchers at the University of Arizona set the germophobic world on fire with a report that said the average shoe sole is covered with 421,000 bacteria and that 90 percent of those bacteria transfer directly to a clean tile floor on first contact. A 2017 study on shoe bacteria by the University of Houston showed that more than 26 percent of shoes examined test positive for C. diff, a bacteria that causes a potentially deadly super diarrhoea. That’s more than triple the amount typically found in kitchens and bathrooms.
While these study statistics make it sound like all shoes are harbingers of death, they don’t tell the whole story. Everyone needs to calm down and put their shoes back on, according to Amesh Adalja, senior scholar at the John Hopkins Center for Health Security and an expert on infectious diseases.
"Just taking off your shoes isn’t really going to substantially diminish that microbial load you have in your house – nor would you want it to, because a lot of times, 99 percent of the microorganisms on the planet don’t do any harm," Adalja tells me. "I find that the general public is often hung up on this concern of keeping everything as sterile as possible, not realising that the floors in your house are [already] teeming with microorganisms [such as] bacteria and viruses."
While some of these bacteria could be harmful under certain circumstances, they’re mixed in with many more that benefit us by strengthening our immunity and helping our digestion. A 2014 study that imagined an Earth without bacteria presented it as a dark, virus-ridden world of constipation and unprocessed biological waste. Adalja also pointed out the fallacy of presuming that taking off your shoes means you won’t be tracking bacteria indoors when you walk around.
"I mean, there's lots of pathogenic material on your socks," Adalja says. "Should you take those off too? And then there’s bacteria on the skin of your feet – what are you going to do, take your skin off? I really think this is a misguided attempt, and not understanding that the planet is dominated by microbial organisms. There’s no reason to oversterilise it."
A recent study of the germiest, most bacteria-ridden places in your home pointed to a bunch of areas you’re probably not putting your shoes or bare feet anywhere near. The 2011 NSF International study identified kitchen sinks, cutting boards, kitchen counters sponges and toothbrush holders as favourite party spots for the bacterial colonies that include salmonella and E. coli.
So some bacteria you drag in on your shoes could actually be good?
Bacteria exist almost everywhere, and that’s for the best. A 2014 study projected that life on Earth would continue in the absence of microbes, but only in a way that was "incomprehensibly bad". Still, Adalja says that unless you have a compromised immune system from a medical condition, you don’t need to start hosing down your kitchen with bleach.
"If you swab around a person’s house," says Adalja. "You’ll find all the scary bacteria that you think about, but that doesn’t mean that you’re going to get infected by them.” Adalja says our immune system, including our skin, is highly skilled at keeping these pathogens from making us sick. He does admit that those with a compromised immune system from things like AIDS, a recent organ transplant, or chemotherapy treatments are more susceptible.
Just use good, regular hygiene, he says, along with your common sense. If you get a cut, put some antibiotic ointment and a bandage on it and keep it moving. "It’s not like you’re going to be getting infections from your couch," he adds. "Energy seems to be very misplaced on just worrying about things in your house when you’re constantly out in the environment dealing with bacteria all the time, and people are very resilient to them."
What if I have a kid crawling around the house? Does this warrant the no-shoes rule?
As far as protecting your precious offspring from things like shoe germs, Adalja says you’re not doing your kids' immune systems any favours by keeping them in an oversterilised environment. He believes that it’s one of the factors driving widespread antibiotic resistance, and that "dirty kids" are actually more likely to grow up healthy.
"We know from something called the hygiene hypothesis that the more sterile the environment – the cleaner the environment the child is raised in – the more likely they are as adults and adolescents to get autoimmune diseases, allergic diseases, things like asthma, eczema," he says.
Adalja is so unafraid of the bacteria on a shoe-trodden floor that he has extended the five second rule to the "15-minute rule" for himself. "You've got your piece of bologna on a plate. Do you not think there are bacteria in the air that are landing on it? Unless you’re dropping it into something that you know is toxic or something that’s got rocks and dirt on it... I don’t see that as a reason to throw the food away."
Adalja says the only reason he would tell someone to take their shoes off indoors would be for aesthetic reasons, like tracking dirt or mud on a white carpet. And honestly, could you really live with yourself if you had a white carpet? This isn't 1980s Miami and you’re not Scarface.
I’m still paranoid. Under what circumstances could shoe-bacteria make me sick?
If you happen to be rehearsing your STOMP audition in an E.coli-contaminated lettuce field and then drive directly to your friend’s apartment and give an encore in her living room, and then you and the gals decide to eat Tapas directly off the floor, someone could get sick.
But unless you’re spending the day traipsing around in cow poo and then doing an extensive soft-shoe performance in your living room or coming home from a long day at the rat poison factory and kicking your work shoes up on the kitchen table to relax, the worst case scenario is probably that the gum you stepped on outside transfers to your carpet.
A version of this article originally appeared on Tonic