What to Wear in the Sauna (And Why It Matters More Than You Think)

By Andrew Havill, Co-Founder & CEO of QUOR

The underwear industry has spent decades optimizing for one thing. Athletic performance. Moisture-wicking polyester, four-way stretch nylon, compression-fit spandex. Every major brand is engineering underwear to move with you, dry faster, and feel like a second skin. From a purely athletic standpoint, they've done a capable job.

The health standpoint is a different conversation. These synthetic fabrics are petroleum-based plastics, pressed against the most temperature-sensitive tissue in the male body for sixteen hours a day, then walked into a 200°F sauna in the same gear.

If you read our earlier piece on how heat exposure affects male fertility, you already know that scrotal temperature is tightly linked to sperm health. What you wear in the sauna matters. What you wear the rest of the day matters just as much. And the question of what you're doing to actively cool the groin during a sauna session is one almost nobody is asking.

The Synthetic Problem

Polyester, nylon, and conventional elastane share a list of properties that make them a poor choice for the fabric closest to reproductive tissue.

They trap heat against the skin instead of letting it dissipate. They create a micro-insulation layer that interferes with the body's natural cooling through sweat evaporation. They shed microplastic fibers with every wear and every wash, and that shedding accelerates with heat, moisture, and friction. The skin of the scrotum is thin, highly vascularized, and more permeable than most tissue on the body, which makes it a meaningful surface for whatever the fabric is releasing.

This isn't just a sauna problem. The average man wears underwear for fourteen to sixteen hours a day. If those are synthetic boxer briefs, that's fourteen to sixteen hours of restricted airflow and synthetic fiber in constant contact with the groin. Day after day. Month after month.

The research on underwear choice and testicular function is real. A 2018 study published in Human Reproduction by Mínguez-Alarcón and colleagues followed 656 men attending a fertility center. Those who wore loose boxers had 25% higher sperm concentration and 17% higher total sperm count compared to men in tighter styles. They also showed lower FSH levels, a hormonal marker associated with testicular compensation. The researchers interpreted this as consistent with the hypothesis that scrotal heat exposure from tight underwear affects spermatogenesis.

Now take those same synthetic fabrics into a 200°F sauna. The underlying variables amplify together. More fiber shedding under heat stress, more trapped thermal load against tissue that's already running above its preferred temperature range.

The answer isn't better synthetics. The answer is to move away from them, especially against the parts of the body that matter most.

Why Cooling Your Groin Changes the Math

Here's the part almost nobody is discussing, and it might be the most important piece of this article.

The whole point of the sauna is heat exposure. The cardiovascular benefits, the heat shock protein activation, the deep sweat, the mental clarity. The research on sauna use and longevity is compelling. A landmark 2015 study in JAMA Internal Medicine found that men who used the sauna four to seven times per week had significantly lower risk of fatal cardiovascular events and all-cause mortality. You don't want to stop saunaing. The benefits are real.

But the testes weren't designed to handle those temperatures. Healthy sperm production requires scrotal temperatures roughly 4°F below core body temperature. That's why the testes sit outside the body in the first place. When you expose them to 185°F sauna air with no protection, scrotal temperature rises quickly. The 2013 Garolla study published in Human Reproduction documented scrotal temperature increases within minutes of sauna entry, with measurable declines in sperm count, motility, DNA integrity, and mitochondrial function after sustained exposure.

So the question becomes: how do you get the full-body benefits of the sauna while keeping the reproductive system protected?

The answer is targeted cooling. Specifically, cooling the groin area during the sauna session.

The concept is straightforward. If heat is the problem, localized cold is the solution. You don't have to cool your entire body. You just have to keep the groin in a safe thermal range while the rest of your body absorbs the heat. This is the principle behind why men who track their fertility markers carefully (including some well-known longevity researchers who test their own biomarkers publicly) have started experimenting with targeted cooling protocols during heat exposure.

Research on this specific protocol is still early. What we can say with confidence is that the physiological logic holds. Cool the tissue that needs to stay cool. Heat the tissue that benefits from heat. The sauna doesn't have to be an all-or-nothing proposition for your reproductive system.

Why DIY Cooling Falls Apart

Once men learn about scrotal cooling in the sauna, the first instinct is to improvise. A cold towel. A generic ice pack. Sitting on something cold. The instinct is right. The execution is where it falls apart.

A cold towel warms within minutes in a 200°F sauna. It provides almost no sustained cooling and you're constantly re-soaking and wringing it out. That's not a sauna session. It's a chore.

A generic ice pack on your lap doesn't stay in place. You're holding it with your hands, adjusting every time you shift position, and it's sliding on sweaty skin. It pulls you out of the recovery-focused mindset that makes the sauna valuable in the first place.

A bag of ice melts fast, leaks water, and creates a mess on the bench.

Going nude does nothing to protect from heat. The testes are fully exposed to the same air temperature as the rest of the body.

Regular cotton boxers are better than synthetics for everyday wear, but they're passive in the sauna. They don't cool anything. They're just fabric sitting between skin and 200°F air. Better than plastic, yes. Solving the problem, no.

Every one of these solutions fails for the same reason. None of them were designed for targeted scrotal cooling during a sauna session. They're improvised workarounds that require active management instead of letting you actually enjoy your session.

How QUOR Approaches the Problem

This is the specific problem QUOR was built to solve. How does a man who saunas regularly protect his reproductive health without giving up the practice that benefits every other system in his body?

The answer required three elements working together.

Premium materials all day. The body of the QUOR Performance Boxer is 95% TENCEL Lyocell and 5% BPA-free elastane. TENCEL is a cellulose fiber produced in a closed-loop process from sustainably sourced eucalyptus wood. It's naturally moisture-wicking, antibacterial, and thermoregulating. It doesn't shed microplastics. The elastane gives the garment the recovery it needs to hold its shape through a full day and many wash cycles.

100% TENCEL where it counts. The inner pouch, the part of the garment that sits against the most sensitive tissue, is 100% TENCEL Lyocell with no stretch fiber at all. No synthetics. No microplastic shedding potential. No chemical load. The logic is simple. The stretch blend handles the engineering problem of fit. The pure TENCEL pouch handles the biological problem of what's touching reproductive tissue for sixteen hours a day.

A pouch designed to hold a targeted cooling insert. The inner pouch is shaped to hold the QUOR CryoInsert, a BPA-free cooling insert with a clean gel formula. You freeze it before your sauna, slide it into the pouch, and it stays hands-free for the duration of your session. No holding anything. No adjusting. No melting ice bags on the bench. Targeted cooling where it matters, while the rest of your body gets the full benefit of the heat.

The CryoInsert is available as a 2-pack, and it comes included in our Essentials Kit and Complete Kit alongside the Performance Boxer. One system built around one specific problem.

Practical Principles for Your Sauna Routine

A few additional principles worth keeping in mind.

Cool down after. A cold plunge or cold shower post-sauna brings core body temperature back to baseline faster. If you're already doing contrast therapy, you're ahead of the game.

Keep it clean. Shower before you enter. Sit on a towel. Don't wear what you trained in without changing first. Basic hygiene that protects you and anyone sharing the space.

Consider a sauna hat. Wool or felt sauna hats insulate your head from the most intense heat at the ceiling of the sauna, where hot air collects. They let you stay comfortable longer and extend sessions safely.

Skip the metal. Jewelry, watches, and piercings heat fast in a sauna and can burn skin. Leave them in the locker.

Think long-term. A single sauna session isn't going to affect your fertility. But the compounding effect of daily synthetic underwear, regular sauna use, and other heat sources adds up over months and years. Small choices compound.

The Bottom Line

What you wear in the sauna isn't just modesty or etiquette. It's a health decision. And what you're doing to actively protect the groin during the session is as consequential as the fabric you're wearing.

The path forward is straightforward. Move away from synthetics for the fabric closest to reproductive tissue. Wear cellulose-based materials all day. When you step into the sauna, have targeted cooling in place, hands-free, where it matters most.

That's the standard QUOR was built around.

This is part of an ongoing series at The QUOR Journal on materials science, male health, and what separates deliberate choices from default ones. Subscribe for the next piece.

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Sources:

• Laukkanen, T., et al. (2015). Association Between Sauna Bathing and Fatal Cardiovascular and All-Cause Mortality Events. JAMA Internal Medicine, 175(4), 542–548.
• Garolla, A., et al. (2013). Seminal and molecular evidence that sauna exposure affects human spermatogenesis. Human Reproduction, 28(4), 877–885.
• Mínguez-Alarcón, L., et al. (2018). Type of underwear worn and markers of testicular function among men attending a fertility center. Human Reproduction, 33(9), 1749–1756.
• Jung, A., et al. (2005). Genital heat stress in men of an infertile couple. International Journal of Andrology, 28(Suppl 1), 37.
• Napper, I.E. & Thompson, R.C. (2016). Release of synthetic microplastic plastic fibres from domestic washing machines. Marine Pollution Bulletin, 112(1-2), 39–45.

Andrew Havill is Co-Founder & CEO of QUOR, a men's vitality brand built around thermal defense. He saunas almost daily and built QUOR because the product he needed didn't exist. Learn more at quorwellness.com.