Can You Wear Underwear in a Sauna? What You Should Know

The Short Answer: Yes, You Can

There is no universal rule against wearing underwear in a sauna. The vast majority of public saunas worldwide — gyms, hotels, spas, health clubs — either allow or actively expect you to wear some form of clothing, whether that's underwear, a swimsuit, or a towel.

In Finland, the birthplace of the sauna, going nude is traditional. But even there, public and hotel saunas often have different norms. In North America, the UK, Australia, and most of Asia, wearing underwear or swimwear in a sauna is standard practice.

Sauna Etiquette Around the World

Sauna norms vary dramatically by culture:

• Finland & Scandinavia: Nudity is traditional and normal. Men and women typically sauna separately. A small towel may be used to sit on.
• Germany & Austria: Mixed-gender nude saunas are common. Textilsauna (clothing-optional) sessions exist but are the exception.
• USA, UK, Australia, Canada: Wearing underwear, swimwear, or a towel is the standard. Most gym saunas require at least a towel.
• Japan: Sentō and onsen have strict no-clothing rules, but dry saunas in gyms may allow towels.
• Middle East & Asia: Swimwear or underwear is typically required.

When in doubt, ask. Every sauna has its own norms, and respecting them is part of the experience.

What Happens When You Wear Underwear in a Sauna

When you step into a sauna heated to 70–100°C (158–212°F), your body begins a cascade of physiological responses. Your core temperature rises, blood vessels dilate, and you start sweating heavily. Here's what happens specifically in the underwear zone:

1. Temperature Rises Fast

Your testicles are designed to operate at 34–35°C (93–95°F) — about 2–3 degrees below core body temperature. In a 90°C sauna, scrotal temperature can rise above 37°C within minutes, pushing well outside the safe zone for sperm production.

A landmark 2013 study by Garolla et al. in the Journal of Urology found that men who used a sauna twice weekly for just 3 months showed significantly impaired sperm motility and morphology. Recovery took 3–6 months after discontinuing.

2. Regular Underwear Traps Heat

Regular cotton underwear, while breathable compared to synthetics, doesn't provide any active cooling. In fact, it can trap heat against your body — especially if it fits snugly. Synthetic materials like polyester, nylon, or elastane are even worse: they block airflow and create a greenhouse effect.

3. Sweat Accumulation

In a 15-minute sauna session, you can lose 0.5–1 liter of sweat. Regular underwear absorbs this moisture, becoming damp and uncomfortable. This doesn't cause health problems, but it makes the experience less pleasant.

The Fertility Factor: Why It Matters More Than You Think

If you're a man of reproductive age who uses saunas regularly, the heat exposure question isn't just academic. Here's what the research shows:

The good news? These effects are reversible. The bad news? Most men have no idea this is happening. If you're trying to conceive — or plan to in the future — the sauna heat question becomes genuinely important.

What to Wear in a Sauna: Your Options Compared

Why Regular Underwear Isn't Enough

Cotton is the best conventional fabric for sauna use — it's breathable, natural, and handles heat well. But breathable doesn't mean cooling.In a 90°C sauna, breathable cotton underwear still lets 90°C air reach your skin. It doesn't actively lower the temperature.

Synthetic fabrics (polyester, nylon, elastane blends) are actively worse. They trap heat and moisture, creating a microclimate that's even hotter than the surrounding sauna air. If your underwear contains synthetics — and most modern "performance" underwear does — you could be making the problem worse.

5 Tips for Wearing Underwear in a Sauna

1. 1. Choose 100% cotton — avoid polyester, nylon, and elastane blends that trap heat.
2. 2. Wear loose-fitting styles — boxer briefs or boxers allow better airflow than tight briefs.
3. 3. Bring a spare pair — change into dry underwear after your session to avoid chafing.
4. 4. Stay hydrated — you'll lose significant water through sweat regardless of what you wear.
5. 5. Consider active cooling — if you sauna regularly, specialized ice pack underwear provides both comfort and fertility protection that regular underwear can't match.

The Bryan Johnson Protocol

Bryan Johnson, the biohacker spending $2M/year on age reversal, popularized the concept of testicular cooling during sauna sessions. His protocol involves applying ice packs to the scrotal area during heat exposure to maintain fertility-safe temperatures.

The challenge? Holding an ice pack in place while sitting in a sauna is awkward, messy, and impractical. That's exactly the problem IcedBallz solves — with a built-in ice pocket in premium cotton underwear that keeps the frozen pack securely in place for 45–60 minutes.

Common Myths About Underwear in Saunas

What We Recommend

If you're going to wear underwear in a sauna — and most people do — make it count. Wear 100% cotton. Avoid synthetics. And if you sauna regularly, consider specialized cooling underwear that actively protects your fertility while making the experience dramatically more comfortable.

IcedBallzis premium cotton underwear with a built-in ice pack pocket. Freeze the anatomically shaped ice pack, slide it in, and enjoy 45–60 minutes of targeted cooling — even in a 90°C sauna. It's $69 + shipping ($6.95 US / $5.95 worldwide), and it works session after session.

References

1. 1. Garolla, A. et al. (2013). "Semen and sperm quality after sauna use." Journal of Urology, 190(4), 1335-1340.
2. 2. Jung, A. & Schuppe, H.C. (2007). "Influence of genital heat stress on semen quality in humans." Andrologia, 39(6), 253-262.
3. 3. Mieusset, R. & Bujan, L. (1995). "Testicular heating and its possible contributions to male infertility." International Journal of Andrology, 18(4), 169-174.
4. 4. Shefi, S. et al. (2007). "The effect of heat on male fertility." Reviews in Urology, 9(2), 85-91.
5. 5. Saunan, P. et al. (2003). "Thermal effects of sauna on the male reproductive system." Human Reproduction, 28(4), 877-882.