A Deeper Look at Footwear and Toxic Exposure

By: Nick Sienkiewicz, DPT, CSCS

You guys know I can’t go too long without talking about feet and footwear. Whether it’s in the clinic or here on this blog, you’ve probably heard me ramble about the impact shoes have on our health. But today, I want to step away from the usual topics of foot mechanics and injury prevention. Instead, I’d like to share a more theoretical yet increasingly relevant perspective that has resurfaced for me after working with a few patients in recent weeks.

Here’s the big idea: Our footwear might be a significant source of toxicity in the modern world. 

Feet: Highly Absorbent & Always Connected 

Human feet are one of the most absorbent and permeable areas of the body. That makes sense when you think about it. Our feet are our constant connection to the Earth. They help us gather information about our environment, much like our eyes and nose. And just like toxins can irritate or damage those sensory organs, I believe our feet may be particularly vulnerable to harmful substances in the materials we wear.

Combine that with the fact that most people spend nearly all day shod (a fancy word for wearing shoes), and the potential impact becomes clear.

What We Know (and Don’t Know) About Clothing & Chemicals 

We already know synthetic fibers in clothing can negatively affect the body. For example, studies as far back as 1992 showed polyester underwear could act as a contraceptive for men. Research on clothing above the ankle is fairly abundant, but when it comes to footwear, the data is far more limited.

 Still, the logic holds. Shoes are made with many of the same synthetic fibers, plastics, glues, and dyes used in clothing. Socks, too, often contain polyester and other synthetic blends. So it’s not far-fetched to suggest footwear could be an overlooked source of chemical exposure.

Clues from Research & Real-World Observations 

 While the science is still young, a few studies and reports raise important questions:

 • Occupational exposure: Shoe factory workers have been documented (1976, 1983) developing toxic polyneuropathy due to chemical exposure in shoe manufacturing.

 • Environmental impact: Recent studies show microplastics from shoe soles leech into soil, increasing oxidative stress in plants. If shoes can off-gas chemicals externally, what happens internally to the foot inside them?

 • Skin reactions: Case studies confirm that allergic contact dermatitis of the feet can result from chemicals in shoe components.

 • Social buzz: There’s even been viral concern around Crocs in hot weather, with claims that heat accelerates the leeching of toxic particles into the skin.

 • Industry secrecy: A 2023 report found that 9 of 16 popular shoe brands contained illegal levels of harmful substances. Yet, thanks to loose regulations, footwear companies often face little to no accountability.

Individually, these findings may not paint a complete picture. But taken together, they suggest a pattern we shouldn’t ignore.

Practical Steps to Reduce Footwear Toxins  

I don’t believe we need to “wait for the science” to make smart choices here. Simple, practical adjustments can help reduce exposure and support healthier feet:

 1. Go barefoot whenever possible. 

This isn’t about walking into the grocery store shoeless—but spending more time barefoot at home, in the yard, or at the beach. Going shoeless reduces potential exposure and offers the bonus of Earthing (natural grounding with the Earth’s frequencies).

 2. Choose natural fibers for socks. 

Organic cotton, wool, and other natural materials provide a healthier barrier than synthetics.

 3. Seek footwear made with natural materials. 

Brands like Vivobarefoot and other minimalist companies are transparent about materials, but even if barefoot-style shoes aren’t for you, look for leather, wool, cotton, latex, or plant-based materials when possible.

 4. Save athletic/performance shoes for performance. 

High-tech athletic shoes are often loaded with chemicals. Use them for training or competition, not as your all-day footwear.

 5. Don’t stress out. 

The goal isn’t to panic or toss every pair of shoes you own. Footwear toxins are just one piece of the larger puzzle of environmental exposure. Do what feels practical and sustainable for you.

The Bottom Line 

The evidence isn’t conclusive yet but logic, preliminary research, and industry reports all point in the same direction: footwear could be a bigger source of toxic exposure than we realize. Taking small steps to reduce that exposure literally and figuratively can support long-term health.

So maybe it’s time we start thinking differently about our shoes. Not just how they look. Not just how they feel. But also what they might be doing to us.