What to Wear in a Sauna (And What Not to)

The short answer: as little as you're comfortable with, made from natural fiber or nothing synthetic at all. There's no required sauna uniform. What matters is that whatever's against your skin can handle 150–190°F heat without trapping moisture, melting, or heating up faster than your body can tolerate. Beyond that, it's mostly a question of personal comfort and where you're sauna-ing.

The traditional answer: nothing at all

In Finland, where the sauna tradition originated, going in nude is the cultural default, not because of any ritual significance, but because it's simply the most practical way to sauna. No fabric to trap sweat against skin, no swimsuit fabric heating up unevenly, nothing to wash and dry after every session. Public and private saunas in Finland are typically single-sex or family-only specifically so nudity isn't a social complication.

This is a cultural norm, not a rule. If you're building a home sauna in the US, you're setting the standard for your own household: nude use, swimsuit, towel, whatever your family or the people you invite in are comfortable with.

What actually works well

A towel. The most common choice for home and mixed-company use. Sit on it (protects the bench and keeps your skin off a surface that's been absorbing heat), wrap it around you, or both. Simple, breathable, and it doubles as what you dry off with when you step out.

A swimsuit. Fine for a sauna, with one caveat: synthetic swim fabric (nylon, spandex, polyester blends) traps heat and moisture against skin in a way that natural fiber doesn't. It's not dangerous in the sense of an acute injury, just less comfortable over a longer session, and it takes longer to dry out afterward, which matters if you're doing multiple rounds. There's also a chemical exposure angle worth knowing about, covered in more detail below.

Loose cotton or linen. A T-shirt and shorts, or a simple robe, work well if you'd rather not be nude or in a swimsuit. Natural fiber breathes and doesn't hold heat the way synthetics do.

Nothing. Traditional, practical, and the standard in Finnish sauna culture for exactly the reasons above.

What to leave outside the sauna

Metal jewelry. Rings, necklaces, watches, piercings. Metal conducts and holds heat far faster than skin does, and a ring that's been sitting at 180°F for ten minutes can genuinely burn you. Take it off before you go in, every time.

Phones, watches, and electronics. Heat and humidity at sauna levels aren't what these devices are built for. Leave them in the changing area.

Synthetic athletic wear. The moisture-wicking fabrics designed for a gym workout are the wrong tool here. They're built to move sweat away from skin during motion, not to sit still in extreme, sustained heat, and they can trap heat unevenly against skin. There's also a more specific reason to skip them in a sauna, and it isn't just about comfort. See "The microplastics question" below.

Makeup and lotion. Both can clog pores right when your skin is trying to sweat freely, and some ingredients aren't pleasant when heated. A clean, product-free face and body is the better starting point for a real sauna session.

Glasses (for long sessions). Not dangerous, but the heat and steam will fog and eventually warp certain frame materials over repeated exposure. Fine for a quick session; worth removing for a longer one.

The microplastics question

There's a real research thread here beyond "synthetic fabric feels less comfortable in the heat," and it's worth knowing about even though no study has looked at a sauna specifically.

Researchers at the University of Birmingham (Dr. Ovokeroye Abafe and Dr. Mohamed Abdallah) have published two relevant studies. The first, in Environmental Science & Technology (2023), found that human sweat, particularly the oily sebum component in it, actively leaches brominated flame retardant chemicals out of common plastics, including polyethylene and polypropylene, the same polymer families used in a lot of synthetic apparel and swimwear. The follow-up study, published in Environment International (2024) using 3D human skin models, went further: it measured actual dermal uptake and found that as much as 8% of the chemical released could be absorbed through skin, with more hydrated, "sweatier" skin absorbing more of it than dry skin (University of Birmingham, 2024).

Neither study put a subject in a sauna. But the mechanism they identified, heavy sweating against skin in contact with plastic-based material, describes a sauna session about as well as it describes anything: sustained heat, real sweat volume, and (if you're wearing a synthetic swimsuit or moisture-wicking fabric) sustained skin contact with the same polymer families the researchers tested. It's a reasonable extension of real, peer-reviewed findings, not an established fact about sauna use specifically, and it's one more point in favor of natural fiber, a towel, or nothing at all.

Quick reference

Wear this	Skip this
Towel	Metal jewelry
Loose cotton or linen	Synthetic athletic wear
Swimsuit (natural fiber preferred)	Phones, watches, electronics
Nothing (traditional)	Makeup or heavy lotion

A note on public vs. private saunas

If you're using a shared or commercial sauna, a gym, spa, or wellness facility, check the posted house rules. Some require a swimsuit at minimum for shared-space etiquette; others follow the Finnish nude-and-towel norm in single-sex settings. A home sauna gives you the freedom to set whatever standard works for the people actually using it.

FAQ

Can you wear a t-shirt in a sauna?

Yes, as long as it's cotton or another natural fiber. Synthetic materials trap heat and moisture less comfortably and can hold onto sweat odor more than natural fibers do.

Is it bad to wear jewelry in a sauna?

Yes. Metal jewelry heats up much faster than skin and can cause burns during a session. Remove rings, necklaces, and watches before you go in.

Do you have to sauna nude?

No. Nude sauna use is a Finnish cultural tradition, not a requirement. A towel, swimsuit, or loose clothing all work fine.

Can you wear a bathing suit in a sauna?

Yes, though synthetic swim fabric traps more heat and moisture against skin than natural fiber. It's a common and acceptable choice, just slightly less comfortable on longer sessions.

Should you take off glasses in a sauna?

For a short session it's not necessary. For a longer session, removing them avoids fogging and reduces wear on frames from repeated heat exposure.

Do synthetic fabrics release microplastics or chemicals in a sauna?

No study has tested a sauna specifically, but University of Birmingham research has found that sweat, especially oily sebum, leaches flame retardant chemicals out of common plastics like polyethylene and polypropylene, and that more hydrated, sweatier skin absorbs more of what's released. A sauna produces exactly those conditions, so it's a reasonable extra argument for natural fiber over synthetic fabric, even though the research wasn't conducted in a sauna setting.

Setting up a sauna where your household makes its own rules? See how a barrel sauna fits your space, or request a quote to talk through sizing and stove options.