Why You Should Never Wear Plastic Fabrics in the Sauna

(And What to Wear Instead by Emma Bianco, Founder, Pure Earth Collection)

Almost all swimwear sold globally is made from plastic-based synthetic fabrics like polyester, nylon and spandex and when these materials are exposed to heat and sweat, they can work against the very benefits you’re trying to achieve.

Saunas are designed to help the body detox, relax muscles and support overall wellbeing. But what many people don’t realise is that what you wear in the sauna matters just as much as the heat itself.

Here’s why plastic fabrics should not be worn in the sauna, what the science says, and how to make a safer choice for your body and your family.

Most Swimwear Is Made From Plastic

The vast majority of conventional swimwear is made from synthetic fibres such as:

Polyester
Nylon
Spandex / elastane

These fabrics are petroleum-derived plastics. In their raw form, plastics are rigid and brittle, so manufacturers add chemicals to make them soft, stretchy and durable enough to be worn against the skin.

These chemical additives often include:

PFAS (“forever chemicals”)
Phthalates (linked to hormone disruption)
Formaldehyde (used for anti-crease and anti-mould finishes)

While these treatments improve performance on paper, they come at a cost to human health, especially when exposed to heat and sweat, as happens in a sauna.

Synthetic Fabrics Have Doubled in the Last 40 Years

To understand the scale of the issue, it helps to zoom out.

In the 1980s, roughly 30% of global textile production was synthetic.
Today, that figure sits at around 70%.

This means our daily exposure to plastic fabrics, through clothing, bedding, swimwear and sportswear is higher than at any point in human history.

And with increased exposure comes increased risk.

Why Plastic Fabrics Are Harmful to Health

1. They Trap Heat and Moisture

Synthetic fabrics are not breathable. They trap heat and moisture against the skin, which can:

Disrupt natural temperature regulation
Encourage bacterial growth
Cause skin irritation and rashes
Increase the risk of infections, particularly in intimate areas

In a sauna, where body temperature and sweating are already elevated, this effect is intensified.

2. Chemicals and Microplastics Are Absorbed Through the Skin

Research shows that microplastics and chemical additives can be absorbed through the skin, entering the bloodstream.

Even more concerning, studies indicate that absorption increases significantly when we sweat. Research has shown that the sweatier the skin, the higher concentration of chemicals are absorbed. This means wearing plastic fabrics during activities involving heat, like sauna use, can fast-track chemical exposure.

3. Plastic Fabrics Increase Toxic Load

Microplastics have now been found in:

Blood
Lungs
Heart
Liver
Placenta
Brain tissue
And other major body parts including main arteries

Once inside the body, these particles can:

Trigger inflammation
Disrupt hormone signalling
Break down and release the chemicals they carry

Over time, this contributes to a growing toxic load, which the body then has to work harder to manage.

4. Electrostatic Effects and Reproductive Health

Synthetic fabrics also create electrostatic fields. Research has shown that prolonged exposure to polyester underwear caused infertility in 100% of dogs and humans studied over extended periods.While more research is ongoing, these findings raise serious concerns about long-term exposure to plastic textiles, particularly in intimate areas.

Why This Matters Even More in the Sauna

Saunas create the perfect storm for increased absorption:

Heat opens the pores
Sweating increases skin permeability
Prolonged contact with fabric
High-friction areas

In simple terms: saunas amplify the risks of plastic fabrics.

If your goal is detoxification, wearing plastic swimwear can undermine the process.

What You Can Do Instead

You don’t need to overhaul everything overnight. Start with the areas that matter most.

Choose Natural Fabrics – Especially for Heat & Sweat

Prioritise natural fibres for:

Swimwear
Sauna wear
Underwear
Gym and activewear

Look for:

Organic cotton
Linen
Wool (for outer layers)
Certified low-tox materials

If synthetic fabrics can’t be avoided entirely, reduce how long you wear them and avoid wearing them when sweating or exposed to heat.

The World’s First Organic Cotton Swimwear for the Whole Family

When I began searching for plastic-free swimwear for me and my children, I discovered something shocking: it didn’t exist.

There wasn’t a single brand offering swimwear made primarily from natural fabrics.

As the founder of a plastic-free children’s brand, and someone deeply passionate about reducing toxic exposure for families, I knew this had to change.After years of development and testing, in 2024 we launched the world’s first organic cotton swimwear range for the whole family.