Finnish men sat in 80 to 100 degree Celsius saunas wearing a thin linen cloth, a felted wool hat, or nothing at all. The sauna was a working building, not a health club amenity. Families heated it, threw water on the stones, and sat in the steam. Every textile in that room earned its place by how it behaved when it got hot and wet.
The modern gym sauna turns what to wear in a sauna into an etiquette question. Towel optional. Shorts acceptable. Shower first. That framing misses the more useful question, which is what the fabric itself is doing against your skin while you sit there sweating. The answer matters because the skin in the groin is one of the most permeable patches on the body. Warm, damp, covered skin also absorbs measurably more of whatever touches it. A sauna garment is not a passive layer. It is a heated, sweat-soaked material pressed against highly absorptive skin.
Sauna cultures solved this before polyester existed
Finnish sauna-goers wore a thin linen wrap or nothing. In single-gender family saunas, nudity was normal. Russian banya culture added a felted wool hat to insulate the head from high heat, while men bathed in linen wraps they could rinse and wring out. Turkish hammams used the pestemal, a thin woven cotton towel that dries fast and adds little bulk when wet. Japanese sento and onsen provided a small modesty towel, and inside the sauna most men sat on it or wore nothing.
- Finnish sauna-goers used thin linen or nothing, with single-gender family saunas treating nudity as normal.
- Russian banya culture added felted wool hats for head insulation while men bathed in linen wraps.
- Turkish hammams used the pestemal, a thin woven cotton towel that dries fast.
- Japanese sento and onsen supplied a small modesty towel, and men sat on it or wore nothing inside the sauna.
What is absent from centuries of sauna history is synthetic athletic wear. Polyester was first synthesized in the 1940s and became a commercial clothing fiber in the 1950s. The compression gym short became a default sauna layer only when gym culture moved saunas into fitness centers in the late twentieth century. That is a new experiment in an old room.
The traditional materials share a trait. Linen, thin cotton, and wool are natural fibers that can be boiled, rinsed, and dried without shedding plastic fragments. Linen in particular moves moisture and dries quickly. That matters when you are sitting in a hot room with sweat running down your back.
The groin skin is built to absorb
In 1971, researchers at the University of California tested how much of a compound absorbed through different body sites after a dermal dose. The scrotal skin was near the top of the range. It absorbed far more than the forearm baseline and more than the scalp, forehead, or underarm (Maibach et al., Archives of Environmental Health, 1971). The reason is anatomical. The outer skin layer is thinner there, there are more hair follicles, and the blood supply is richer.
Two more mechanisms stack on top of that. Warm skin absorbs more. In human skin tests, raising skin temperature from 25 to 39 degrees Celsius increased absorption of test compounds by over 200 percent (Toxicology in Vitro, 2020). Damp, covered skin also absorbs more. Occlusion and sweat raise skin hydration, which raises penetration (British Journal of Dermatology, 1988).
In a sauna, all three conditions line up. Fabric choice against that skin becomes a materials decision.
Polyester, cotton, and linen under heat
Polyester
Polyester is durable and dries fast, which is why gym clothes use it. In a sauna, though, you are wearing a plastic fiber against the most permeable skin on your body while temperature and sweat both rise. There is a standardized artificial-sweat migration test called ISO 105-E04. Studies using it have measured real chemistry leaving fabric into sweat. Polyester is manufactured using an antimony catalyst, and trace antimony can migrate out of polyester into sweat (Regulatory Toxicology and Pharmacology, 2021). A 2020 study also showed polyester garments release microfibers into the air during ordinary wear, at levels in the same order of magnitude as washing when scaled (De Falco et al., Environmental Science and Technology, 2020). In a small hot sauna, that air is the air you breathe.
Cotton
Cotton feels soft and natural. The problem is what cotton does with water. Cotton soaks up sweat and holds it against you, staying damp and warm through a hot session (Jhanji et al., Fashion and Textiles, 2015). Heavy cotton terry is a bad sauna choice because it holds moisture and heat for a long time. Thin woven cotton, like a Turkish pestemal or a flat cotton towel, is different. It has less bulk and dries faster, which is why it worked for centuries in hammams.
Linen and modern cellulosics
Linen is the traditional sauna fiber for a reason. It wicks moisture, dries quickly, and does not cling when wet. Modern regenerated cellulose fibers like modal and lyocell also show strong wicking and air permeability in controlled tests (Ozdemir, Journal of Engineered Fibers and Fabrics, 2017, and Kucukali-Ozturk et al., Fibers and Polymers, 2023). When these fibers shed, they release biodegradable cellulose, not persistent plastic microfibers. That distinction matters more than fiber quantity, because some cellulosic knits can shed as much fiber mass as polyester. It is what the shed fiber is made of that differs, not always the amount.
What I would wear in a gym sauna
Most men cannot sit bare in a coed gym sauna, and many would not want to. The practical goal is one thin, loose layer that moves moisture and dries fast.
- A thin linen or Turkish cotton towel wrapped around the waist works well. It keeps a single loose layer against the groin, dries quickly, and lets air move.
- If you need something with more structure, loose linen or fast-drying cellulosic shorts beat polyester compression shorts.
- Sit on a dry towel to avoid direct contact with a hot bench.
- Skip heavy cotton sweatpants and thick cotton t-shirts. Cotton holds water and heat, the opposite of what you want in a sauna.
- Skip a polyester compression base layer as the only thing between the heat and your groin.
The question is whether you want a plastic fiber pressed against highly permeable skin under maximum heat and sweat when better options exist. Read the label. Pick a loose, fast-drying natural or cellulosic layer.
The heat and fertility note most men skip
Heat around the testicles is a real variable for male reproductive health. Sauna-level heat temporarily lowers sperm count and can worsen morphology. The effect reverses once the heat exposure stops, because sperm production needs the testicles a few degrees cooler than core body temperature (Garolla et al., Human Reproduction, 2013). Clothing type and posture also change scrotal temperature. Tighter underwear and sitting raise scrotal temperature relative to looser underwear and movement (Jung et al., Human Reproduction, 2005, and Mieusset et al., Journal of Andrology, 2007). Men reporting looser boxer-style underwear had higher sperm concentration and total count in a fertility-center cohort (Minguez-Alarcon et al., Human Reproduction, 2018).
A sauna is already applying heat. Adding a tight polyester layer over the area stacks more warmth on top. A loose linen or thin cotton wrap lets air move and keeps that area closer to the temperature it prefers than tight, heat-trapping underwear does. That is a physical claim about airflow and temperature, not a fertility guarantee. If you have specific fertility concerns, a doctor who can look at your individual situation is the right person to ask.
This content is for educational purposes only and is not medical advice. Oakman products are designed for physical comfort and cooling. They make no claims about fertility, sperm quality, or hormone levels. Consult a healthcare professional for personalized advice.
Frequently asked questions
what should men wear in a sauna
A thin linen or Turkish cotton towel wrapped around the waist is the most practical choice for most men. It keeps a single loose layer against the groin, dries fast, and lets air move. Loose linen or fast-drying cellulosic shorts work better than polyester compression shorts under heat.
is cotton or polyester better for the sauna
Thin woven cotton works better than heavy cotton terry, but polyester is the one to think hardest about because it sheds plastic microfibers and can release trace antimony into sweat. Linen and modern cellulosic fibers like modal or lyocell wick moisture and dry faster than cotton. When cellulosics shed, the fiber is biodegradable, not persistent plastic.
does sauna heat affect sperm count
Yes, sauna-level heat temporarily lowers sperm count and can worsen morphology, and the effect reverses once heat exposure stops. Clothing that traps more heat around the testicles adds to the problem, while loose breathable layers let air move. If fertility is a concern, talk to a doctor for individual guidance.
can hot sauna clothing make your skin absorb chemicals
The skin in the groin absorbs more than most body sites, and warm damp skin absorbs even more. Fabric chemistry can migrate into sweat under those conditions, so a clean natural or cellulosic layer is a better choice than a heated plastic one. The exposure from a single session is low, but the material choice matters over time.