What Happens When You Sweat in Clothing Made of 100% Plastic?

Think about it: the fabric you wear closest to your skin is plastic. And not just any plastic—these are synthetics like polyester, nylon, and spandex. To make that plastic stretchy, breathable, and moisture-wicking, brands add chemicals: flame retardants, per- and polyfluoroalkyl substances (PFAS), phthalates, and other endocrine disruptors.

Here’s the part most people don’t realize: these chemicals aren’t locked into the fabric. They’re free to migrate.

What happens when you break a sweat? Heat and moisture act like a chemical accelerator. They dissolve and mobilize those additives, sending them straight from your leggings, your sports bra, your workout top, directly into your skin. And your skin is not a barrier—it’s a sponge. Transdermal absorption (yes, that’s the science term) allows these chemicals to bypass digestion and liver filtration and go straight into your bloodstream.

And the research backs this up. Multiple studies and reports show that PFAS are commonly present in synthetic textiles, including athletic wear, and that these chemicals can migrate into sweat and be absorbed through the skin. (see sources referenced at the bottom of this blog)

This isn’t just theory—your intense workout is literally helping these chemicals migrate from fabric into your body.

What can you do? Start by reading labels. Look for natural fibers like organic cotton, bamboo, or recycled wool. Avoid fabrics labeled “waterproof” or “stain-resistant,” because that often signals PFAS treatment. And yes—share this knowledge. Pressure the brands on social media. Spread the word. Every conversation chips away at the idea that “performance gear” has to come at the cost of our health.

Your body is your temple. It deserves clothing that respects it—not chemicals that fight it.

 

Sources: 

  • A Commission for Environmental Cooperation (CEC) report tested over 130 textile items in North America and found PFAS migrate from clothing under simulated sweat conditions. Source 
  • Toxic-Free Future and Environmental Health News documented high levels of fluorine (an indicator of PFAS) in yoga pants, leggings, and sports bras, and lab studies show water-soluble PFAS can leach into artificial sweat during contact. Source 
  • Reviews of textile chemicals confirm that dermal absorption is a meaningful exposure route, especially for persistent chemicals in treated fabrics. Source 
  • Even CPSC white papers highlight that PFAS in fabrics can transfer into sweat, demonstrating a realistic pathway for human exposure. Source