Merino Wool Underwear: The Discovery That Made Me Quit Performance Briefs Forever

Lauryn

Founder, PRIMALS

I Started Researching Merino Wool Underwear. What I Found Was Alarming.

When I started building PRIMALS, I set out to create truly toxin-free alternatives to everyday products. That meant investigating every material, every process, every label. When I got to men's merino wool underwear, I expected to find a clean alternative to synthetics. I did not expect what I actually uncovered.

I pulled up the bestselling "performance" underwear brands and checked their labels. 92% polyester, 8% spandex. Brand after brand after brand. Men are wearing petroleum-based plastic against the most absorbent, most sensitive skin on their bodies, every single day, and nobody is talking about it.

That discovery sent me down a rabbit hole into merino wool underwear, and then into an even darker finding about how "natural" wool brands are hiding plastic and probable carcinogens in their products. Here is the full story.

Most Men's "Performance" Underwear Is Made of Plastic

If the label says polyester, nylon, spandex, or elastane, it is petroleum-based plastic. That is not marketing language. Polyester is literally made from the same raw material as plastic bottles.

When plastic fabric sits against warm, sweating skin, it releases microplastics and chemical compounds directly onto the body. The groin area is one of the most absorbent zones on the entire body. The skin there is thin, vascular, and permeable. What touches it gets absorbed fast.

Heat and friction accelerate this process. Working out, sitting at a desk, sleeping under covers. Every scenario where the body generates warmth breaks down those plastic fibers faster, releasing more chemicals right where it matters most.

Studies have linked polyester underwear specifically to decreased sperm count, lower testosterone levels, and hormonal disruption. The synthetic chemicals in these fabrics mimic estrogen in the body. They are classified as endocrine disruptors. A study published in the European Urology journal found that polyester underwear generated electrostatic charges in the scrotal area that significantly reduced sperm count.

The Superwash Secret Hiding in "Natural" Merino Wool Underwear

The obvious solution seemed to be merino wool. Natural fiber. No plastic. Better for the body. So I started investigating the merino wool underwear brands already on the market.

That is when things got worse.

I started researching how most merino wool brands make their fabric machine-washable. The process is called superwash, and what I found shocked me.

Superwash is a two-step chemical treatment. First, the wool is stripped in a chlorine bath that burns off its natural protective scales. Then it is coated in a plastic resin called Hercosett 125. This resin is made with a chemical called epichlorohydrin.

Epichlorohydrin is classified as a "probable human carcinogen" (Group 2A) by the International Agency for Research on Cancer (IARC) and as a Group B2 probable carcinogen by the EPA. NIOSH recommends it be handled as a human carcinogen based on studies showing increased respiratory cancer deaths in exposed workers.

Let that sink in. Most merino wool underwear brands strip their wool with chlorine, then coat it in a plastic resin made with a probable carcinogen, and market it as "natural." The chlorine process also creates toxic AOX wastewater that poisons aquatic environments.

What Gets Lost When Merino Wool Underwear Gets Superwashed

Wool has remarkable natural properties. Merino wool fibers are covered in lanolin, a natural wax that is antibacterial, moisture-wicking, and temperature regulating. It is what makes wool such an incredible performance fabric without any synthetic engineering.

The superwash process strips all of this away. The chlorine bath removes the scales and the lanolin. The plastic resin coating seals the fiber in synthetic material. The result is a fiber that looks like wool on the label but behaves like a compromised hybrid that has lost the very qualities consumers are paying a premium for.

And it gets worse. I checked the labels on 12 popular "natural" underwear brands. Every single one had elastane or spandex hidden in the waistband. Even the brands that market themselves as 100% merino quietly slip in 5% synthetic material. Still plastic. Still releasing toxins. Still touching skin.

This means the difference between a truly clean product and a chemically processed one is not visible on the surface. It comes down to the manufacturing process that most brands never disclose. If you are shopping for merino wool underwear to avoid plastic and chemicals, you need to know exactly what to look for and what questions to ask before buying.

Ozone: The Chemical-Free Alternative to Superwash

The question I kept coming back to was simple: how do you make merino wool machine-washable without destroying it with chemicals and plastic?

The answer is ozone treatment. It is a cutting-edge process that uses ozone gas to gently smooth the surface of wool fibers, preventing felting and shrinking during washing. No chlorine. No plastic resin. No Hercosett 125. The only byproducts are oxygen and water.

Companies like Patagonia have already started moving toward ozone-based treatments for exactly this reason. It works just as well as superwash without any of the toxic processing. The wool stays 100% natural. The lanolin stays intact. The fiber retains its breathability, moisture-wicking ability, and temperature regulation.

What to Look for When Shopping for Merino Wool Underwear

Check the fabric composition of the body. It should be 100% merino wool with no polyester, nylon, or spandex blended in. Many brands blend in synthetic fibers to cut costs or add stretch, which defeats the entire purpose of choosing a natural fiber.

Check the waistband material. This is where most brands hide their synthetics. Even brands that advertise a merino wool body will use a polyester or elastane waistband. Look for organic cotton and natural rubber as alternatives that provide stretch without synthetic materials.

Ask about the washability treatment. If the wool has been superwash treated, the fiber has been chlorine-stripped and coated in plastic resin. Look for ozone-treated merino wool underwear instead.

The PRIMALS Merino Wool Boxer Briefs: Natural Underwear Without the Toxins

The PRIMALS Merino Wool Boxer Briefs were designed from the ground up to eliminate every source of toxin exposure from men's underwear. No compromises in any component. Here is what makes them different:

Frequently Asked Questions About Merino Wool Underwear

Stop Wearing Plastic. Start Wearing PRIMALS.

You wear underwear for 16+ hours a day, 365 days a year. That is over 5,800 hours per year of direct skin contact with the most absorbent tissue on your body. The science is clear: synthetic fabrics release microplastics, endocrine disruptors, and chemical compounds that accumulate in your tissues over time.

The fix is simple. Switch to underwear that was never made with plastic or chemicals in the first place.

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