How to Protect Your Hair in the Sauna: What Hair Science Says

At head level, a Finnish style sauna is usually 176 to 212°F (80 to 100°C), which overlaps with the hottest setting in one of the most cited hair dryer studies. The air is also very dry. We could not find a single controlled study on sauna use and hair, so this guide sticks to what hair science does show and turns it into simple habits for your next session.

Key takeaways

1. Know the air at head level.
2. Heat roughens the outer layer of hair.
3. Dry air and water both change hair.
4. Be extra careful with colored and bleached hair.
5. Go in damp, not dripping.
6. Keep braids, locs and long hair loose and tucked.
7. Cover up with a wool hat.

1. Know the air at head level

Heat rises, so your head sits in the hottest part of the room. A 2018 review by Laukkanen, Laukkanen and Kunutsor in Mayo Clinic Proceedings gives 176 to 212°F (80 to 100°C) at the level of the bather's head, lower temperatures near the floor and a relative humidity that usually varies from 10 to 20 percent. Throwing water on the stones raises both temperature and humidity for a short time. A typical stay lasts 5 to 20 minutes and is repeated a few times with cooling breaks in between. For your hair, that adds up to three things: real heat for a limited time, very dry air, and a cold shower afterwards. Each one plays a role, as the next sections show. The good news is that each one is easy to manage.

2. Heat roughens the outer layer of hair

The most cited study here is about hair dryers, not saunas. Lee and colleagues (2011, Annals of Dermatology) shampooed and dried tresses of untreated hair once a day for 30 days. They compared air drying with a dryer held at 6, 4 and 2 inches, which meant about 117°F (47°C), 142°F (61°C) and 203°F (95°C) at the hair. Under the electron microscope, damage to the cuticle, the outer protective layer, grew with temperature. The hottest group showed cracks, holes and lost cuticle. The inner cortex was not damaged in any group. Limits: the hair came from a commercial supplier, not from living volunteers, the number of tresses is not reported, and a hot air stream is not the same as sauna air. Still, it shows that the hair surface reacts to heat in the range a sauna reaches.

3. Dry air and water both change hair

Hair constantly takes up and releases water depending on the air around it. In a 2014 article for the trade journal Cosmetics and Toiletries, hair scientist T. A. Evans explains that the water content of hair is overwhelmingly dictated by relative humidity, with hair weight rising by about 22 percent between 0 and 90 percent humidity. Water also changes how hair behaves: it disrupts the hydrogen bonds and ionic bonds that give hair its strength, so wet hair is weaker and swells. In a sauna day, hair goes from very dry hot air to a cold shower and back, several times in an afternoon. That cycle is a plausible reason many people say their ends feel like straw after a long sauna day. It also explains why gentle handling afterwards matters as much as what you do on the bench.

4. Be extra careful with colored and bleached hair

Chemically treated hair seems to react more to heat. In a 2026 study in Biopolymers, Lima and colleagues heated untreated, bleached and acid straightened hair fibers and tracked their structure with X ray scattering and electron microscopy. Bleached and straightened fibers changed more under heat, which the authors link to the loss of protective surface components. The abstract does not report the temperatures or the number of samples, so read it as a direction, not a number. Color can shift with heat too. Nogueira and colleagues (2004, Journal of Cosmetic Science) found that a hot plate at 342°F (172°C) visibly darkened untreated hair, while an hour under a hand dryer at about 140°F (60°C) changed it barely beyond measurement error. The American Academy of Dermatology notes that sun can weaken, dry and fade hair, especially after dyeing or bleaching.

5. Go in damp, not dripping

There is no study comparing wet and dry hair in a sauna, so here is what the lab work suggests. Water weakens hair temporarily, as Evans explains. In the Lee study, the air dried group was the only one that showed swelling in the cell membrane complex, the layer that holds hair cells together. The authors suspected that more than two hours of contact with water did more harm there than the heat. So soaking wet hair for a whole afternoon is not ideal either. A practical middle way:

• Wash out styling products in the shower before the first round.
• Squeeze the water out and wrap your hair in a towel instead of rubbing it, as the American Academy of Dermatology advises.
• Go in with damp, not dripping, hair under a hat.
• Use conditioner after you shampoo at the end of the day.

6. Keep braids, locs and long hair loose and tucked

With long hair, the ends are most exposed, since they tend to lie on hot wood or on your shoulders. Twist long hair into a loose bun and tuck it under the hat. Use a soft hair tie without metal parts, because metal heats up fast. With braids and locs, the main thing is to avoid extra pull. The American Academy of Dermatology recommends looser styles, thicker braids and locs over very thin ones, and pulling hair back loosely under head coverings. It also notes that coverings which rub constantly over tightly pulled hair add strain. In practice, pick a hat with enough room to rest on your hair instead of pressing it down. For lots of hair or dreadlocks we recommend the Pro with its roomier cut. Our guide to sauna hats for big heads shows how to measure.

7. Cover up with a wool hat

A hat is the simplest way to put a layer between your hair and the hottest air in the room. The idea: wool traps still air in its crimped fibers, which slows down heat transfer, and it can absorb roughly 30 to 40 percent of its weight in moisture without feeling wet, as materials scientist Diana Tuulik of Tallinn University of Applied Sciences told the Estonian broadcaster ERR. The Original is a single layer of boiled wool that covers your ears. The Pro adds a second layer, extended ear protection and a sewn brim over forehead and eyes. Many people dip the hat in cold water and wring it out well before the first round. Between rounds, hang it up to air out. Most of the time, that is all the care it needs.

FAQ

Does the sauna damage your hair?

We could not find a controlled study on sauna use and hair. Lab studies show that heat in the sauna range can roughen the cuticle and that repeated wetting and drying stresses hair. Covering it, tucking up long hair and gentle care afterwards reduce how much of that your hair gets.

Should I wear a hat in the sauna to protect my hair?

Many people do, and the reasoning is sound: wool puts an insulating layer between your hair and the hottest air. It will not make your hair heatproof, but the idea is that less heat reaches it directly.

Can I go in the sauna with color treated hair?

Yes. Bleached and chemically treated hair seems to react more to heat in lab studies, so cover it with a hat and tuck up the ends. The American Academy of Dermatology recommends conditioner after every shampoo, which applies to colored hair too.

Find your color in all hats, and learn how to keep your hat fresh in how to wash a wool sauna hat.