The Gross Science 
Explaining Why You Should Take Your Shoes off 
While Indoors

Author: Emily Newton


Think going barefoot indoors is for the posh? Think again — wearing your outdoor shoes in the house may expose you to harmful bacteria, chemicals and allergens.

Although wearing shoes inside is common in the United Kingdom, there are plenty of good reasons to rethink the habit.

Germs

You probably already remove your shoes if you step in something extra nasty or smelly, but did you know that simply walking on the pavement can expose you to contaminants?

A 2022 study found 17.8% of health care workers in a Swiss tertiary care centre had Clostridioides difficile — a bacterium that causes life-threatening diarrhoea — on the soles of their shoes. If you work in health care or frequently visit the doctor, there’s a good chance your shoes are contaminated with bacteria you don’t want to bring home.

You might inadvertently be tracking in Staphylococcus aureus, the culprit behind many cases of skin infections, meningitis, endocarditis and more. The soles of your shoes can also carry Escherichia coli, and some strains of this bacterium can cause intestinal and urinary tract infections. The E. coli O157:H7/STEC strain multiplies rapidly at temperatures above 4.4° Celsius and can cause dangerous food poisoning.

Other shoe- and floor-associated microbes scientists have catalogued include species from the Paracoccus, Rubellimicrobium, Janthinobacterium, Hymenobacter and Rhodobacter genera — and that’s not even a complete list. Your shoes are crawling with germs.

Some of the bacteria on your shoes may be drug resistant, meaning they’re much harder to kill. Antimicrobial-resistant microbes have evolved mechanisms to protect them against substances like disinfectants and antiseptics. That means antibiotics likely won't be as effective if you get an infection from them.

It’s even more important to take your shoes off indoors if you have carpet because it can hold more dust and bacteria than solid floors due to its greater surface area. You should hoover and steam clean your carpet frequently to minimise the risk of bacteria lingering in the fibres.

Harmful Chemicals

If you like to walk in fields, parks, golf courses or gardens, you’re probably stepping in pesticides. The World Health Organisation estimates 385 million cases of pesticide poisoning occur annually worldwide, with around 11,000 deaths as a result.

Toxicity depends on how much you’re exposed to, which type of pesticide it is and whether you have any underlying health problems. Pesticides can cause nose and throat irritation, dizziness, nausea, asthma, reproductive problems and even cancer.

Wearing shoes in the house could also contaminate your home with per- and polyfluoroalkyl substances (PFAS), also known as forever chemicals due to their propensity for persisting in the environment. One study found 26 different types of PFAS in a single street-sweeping sample.

These chemicals are tentatively linked to increased cholesterol levels, changes in liver enzymes, lower baby birth weights, an increased risk of kidney or testicular cancer, decreased vaccine responses in children and an increased risk of high blood pressure in pregnant women. Scientists are still gathering data to determine the full range of health effects.

Asphalt is another substance you might accidentally bring home with you. Fresh asphalt gives off airborne contaminants including particulate matter, oil mist and polycyclic aromatic hydrocarbons. Scientists have linked exposure to new asphalt with irritated eyes and airways, lung and bladder cancer, heart disease and reduced lung function.

Allergens

If anyone in your home reacts to pollen, mould, dust or other outdoor allergens, not wearing shoes in the house could help minimise their symptoms. Wipe your shoes as thoroughly as you can on a doormat before entering. Then, leave them at the door to avoid tracking these harmful substances into your home.
Keeping Children and Pets Safe
It’s imperative to avoid wearing outdoor shoes in the house if you have animals or young children. Because they tend to spend so much time on the floor, they could directly ingest bacteria or chemicals. Puppies are especially prone to licking and biting objects.

Your shoes may even have traces of lead on them if you live in an area with lead-contaminated soil. If you live in an older home, there may be layers of lead paint and lead-containing plaster in the surrounding area.

This toxic metal can contribute to learning and behaviour problems such as reduced IQ, hyperactivity and stunted growth in kids. It also causes serious health problems in children and animals. That’s why it’s crucial to clean your floors frequently and not wear outside shoes in the house.
Are Indoor Shoes OK?
Although it’s best not to wear outdoor shoes inside, it’s completely fine if you have a pair of beloved slippers or shoes you wear solely in the house. It’s not the act of wearing shoes that exposes you to contaminants, but rather that footwear is a vector for moving germs from one place to another. You’d pick up the same germs from strolling barefoot outdoors and then walking back into the house.

In fact, wearing indoor slippers can be helpful for people with particular foot problems. The proper footwear can provide arch support, cushion your feet against the hard floor and keep you warmer in the winter. Just make it a rule to wear your slippers only in the house.
Wearing Shoes in the House Could Be Harmful
Ultimately, it’s your choice whether or not to wear shoes indoors, but it’s probably more beneficial to take them off if you live in a busy urban area and spend a lot of time in public spaces. It could also protect your family from accidentally eating something harmful from the floor. Regardless of your house rules, it’s always a good idea to clean frequently to minimise your exposure to contaminants.

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