We are environmental chemists who have spent a decade examining the indoor environment and the contaminants people are exposed to in their own homes. Although our review of the indoor environment, via our DustSafe program, is far from complete, on the question of whether to put on or take off shoes at home, the science leans towards the latter.

It is best to leave your trash outside the door.

Contaminants in your home

People spend up to 90% of their time indoors, so the question of whether to wear shoes around the house is not trivial.

The policy generally focuses on the outdoor environment for risks related to soil, air quality and environmental public health. But regulatory interest is growing for indoor air quality.

The material that accumulates inside your home doesn’t just include dust and dirt from people and animals shedding hair and skin.

About a third comes from outside, blown or stomped on these offensive shoe soles.

Some of the microorganisms found on shoes and floors are drug-resistant pathogens, including difficult-to-treat hospital-acquired infectious agents (germs).

A roll call of interior villains

Our work has involved measuring and assessing exposure to a range of harmful substances found inside homes, including:

These contaminants – and most importantly, the dangerous nerve lead – are odorless and colorless. So there’s no way to tell if the dangers of lead exposure are only found in your floors or water pipes, or if they’re also on your living room floor.

The most likely reason for this connection is dirt being blown off your yard or stomped on your shoes and on the hairy paws of your adorable pets.

This connection speaks to the priority of making sure that the matter of your external environment stays exactly there (we have tips here).

A recent Wall Street Journal article argued that home shoes aren’t so bad. The author pointed out that E. coli – a dangerous bacterium that thrives in the intestines of many mammals, including humans – is so widespread that it is just about everywhere. So it’s no surprise that it can be dabbed onto shoe soles (96% of shoe soles, as the article points out).

But let’s be clear. While it’s nice to be scientific and stick with the term E. coli, it’s, more simply, the bacteria associated with feces.

Whether it’s ours or Fido’s, it has the potential to make us sick if exposed to high levels. And let’s face it, it’s just gross.

Why wander inside your home if you have a simple alternative: take off your shoes at the door?

All in all, sans shoes wins

So are there any downsides to having a shoeless household?

Beyond the occasional bumped toes, from an environmental health perspective, there aren’t many downsides to having a shoeless home. Leaving your shoes on the entrance mat also leaves potentially harmful pathogens behind.

We all know that prevention is much better than cure and removing shoes at the door is a simple and basic prevention activity for many of us.

Need shoes for foot support? Easy – just have ‘indoor shoes’ that are never worn outside.

There remains the issue of “sterile home syndrome,” which refers to increased rates of allergies in children. Some claim it is linked to overly sterile households.

Indeed, some dirt is likely beneficial because studies have indicated that it helps build your immune system and reduce the risk of allergies.

But there are better and less gross ways to do it than walking around inside with your dirty shoes. Get outside, take a walk in the bush, enjoy the great outdoors.

Just don’t bring the dirtiest parts inside to accumulate and contaminate our homes.

Mark Patrick Taylor is Chief Environmental Scientist at EPA Victoria and Honorary Professor at Macquarie University. It received funding through an Australian Government Citizen Science Grant “A Citizens’ Insight into the Composition and Risks of House Dust” (The DustSafe Project).

Gabriel Filippelli is Chancellor Professor of Earth Sciences and Executive Director of the Institute for Environmental Resilience at Indiana University. He does not work for, consult, own stock, or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond his academic appointment.