Is there even a difference? When totally enclosed in rainwear to stay dry, it is only a matter of time before enough body heat gets trapped under the suit, you start to sweat, and end up soaked by sweat. Or that was the dramatized story of rainwear in the past at least, before innovative breathing materials and designs with ventilation holes and vents become available.

For this article I will take a closer look at the history of the sauna suit, sometimes called an exercise suit or sweat suit, discuss the functional aspects of them, and try to connect it to the rainwear community. A sauna suit is here defined as a suit worn with the purpose of sweating, which is different from rainwear where sweating is just a possible negative by-product. Besides the usual list of sources which will be given at the bottom of the article, I also interviewed a friend who has first-hand experience with sauna suits as an athlete to bring a bit of perspective.
History
When vulcanization was invented and patented by Charles Goodyear in 1844, and rubber became a commercially viable material, a search for applications for this novel material ensued. The waterproof features of rubber made rainwear the obvious choice and both raincoats and rubber boots were the first products made in large quantities. Rubber garden hoses, golf balls, hot water bottles, soles for shoes, and tires for bicycles, and later cars, quickly followed. Below an overview of some of the rubber products produced by the North British Rubber Company in 1924.

The prospect of finding a new application for rubber, and being the first and only supplier of rubber in that specific category, was a luring prospect resulting in lots of inventors starting to experiment. One invention was a clothing item which can be traced back to 1906 when Dr. Jeanne Walter received the patent for a soft rubber garment that was to be worn close to the body.

The text included with the patent filing explains that wearing this soft rubber gear would retain heat and perspiration for therapeutic purposes. The garment would closely fit the body, avoid chafing by being seamless, and make escaping of heat or sweat nearly impossible. What is described here is a sauna suit made out of rubber.

The intended purpose of this rubber garment did not have to be further explained in the patent filing, but the mentioned “therapeutic purpose” was explicitly named in advertisements for Dr. Jeanne Walter’s advertisements: reducing flesh. This gear was basically sold as a weight loss solution where fatty tissue gets burned off by simply letting your body sweat. This idea was pushed to such a level that even smaller rubber items were sold to spot reduce fatty tissue: rubber underwear, bust reducers, and straps you could tie under your chin to remove that second chin. Below an old newspaper advertisement mentioning the flesh reduction and promoting a chin reducer for just $2.

The promotional material of Dr. Jeanne Walter claimed millions of sales by the early twenties and more producers of slimming underwear would flock to the market promising to either burn of fat or at least give the visual impression of less flesh on the body. Below an advertisement from 1934 showing rubber underwear from Charnaux. For much more information, advertisements, and even vintage rubber corrective underwear please take a look at the site of Corsetiere.

Interesting detail in the gear shown above are the small perforations in the rubber to let the skin breath. Over time it must have become clear that wrapping yourself in tight rubber for extended periods of time would degrade the skin and could lead to sores and infections. The holes would prevent this, but that would also make the “sauna effect” much more limited. Maybe that is why the focus shifted from sweating to tightly wrapping the body to create the illusion of being slimmer.
With vinyl becoming the material of choice for many products originally made from rubber in the forties and fifties, also the material of the sauna suit changed. Vinyl was not only much cheaper per square meter; it was also easier to turn into garments with high-frequency welding machines instead of having to glue it by hand. And while the material of choice changed, the promise made to potential customers stayed the same: lose unwanted weight easily by simply wearing the suit during your exercising or even when doing normal chores around the house. Fun fact: at some point even inflatable sauna pants were sold that were supposed to spot reduce fatty tissue, as shown below. The expression on the male model’s face says it all.

And below an advertisement for what would become the most recognizable color scheme for the sauna suit: a silver suit with a red and yellow stripe around the arm.

Sauna suits are still available today. The cheapest ones are easily available in larger sport stores and look very similar to the ones advertised above. More sport-specific ones, often produced in black with brand names printed on them, are being sold online and in specialised stores.

Functionality
The basic promise made in the past by producers of sauna suits was that the wearer would lose weight simply by putting the suit on for some time. Experiments proved that to be false: while you would expend a little more energy trying to regulate your body temperature, this would be negated by slowing down with your exercises due to fatigue or by training for a shorter period of time. That is not to say a sauna suit is completely useless as there are genuine uses for one:
Making weight
Athletes that compete in weight classes sometimes need to shed water weight right before the weight-in and a sauna suit can help here. This is a rather dangerous activity though as you dehydrate your body temporary and this should not be done without proper coaching and supervision!
Intensifying your training
By simply wearing a sauna suit during exercising you can make it harder on yourself so an actual competition feels relatively easy. I have used a sauna suit in the past for this reason where I geared up for a run to get used to running in the heat and to test my perseverance. It actually made me feel pretty confident as I felt like a professional athlete running around suited up even though my running times were nowhere near impressive. The only strange moments were when the sweat would collect near my elbows and I had to hang my arms down every now and then to let all the sweat out which could disturb onlookers.

Relaxation
The final way to use a sauna suit is to mimic the effect of a regular sauna or steam bath. Here you suit up to sweat it out in the hopes you feel better afterwards. There are no proven physical benefits, like detoxing, but it can help mentally as you can relax and just mediate while suited up.

Fetish
Besides that a sauna suit sort of looks like a rainsuit, is often made of the same materials, and the two can be used interchangeably with some success, the real connection between sauna suits and rainwear is in the fetish community where there is some overlap. The sauna suit fetish community, which is part of the larger “sweat fetish” community, can be split into three, not mutually exclusive, groups based on which part of the sweating is interesting to them.

Taste and smell of sweat
A 2018 Pornhub Insights article found that there are 5,000+ sweat-themed videos they host, with 300,000 combined monthly views, and a quick google search shows an active trade going on in the market for “used and sweaty” pieces of clothing, mainly socks and underwear. The focus here is mostly on the smell (osmophilia) and taste of sweat (salophilia). This group of people, who seem to be the majority within the sweat fetish community, have limited overlap with the rainwear community as none of the top 25 searches include anything that can be linked to rainwear. The most viewed sweaty video is about a dirty yoga teacher who is working with a gorgeous fitness model.
Slippery and messy fun
This is mostly about seeing someone get all messy (salophilia) from sweat or the feel of the smooth materials against your own skin. The messy part has some good overlap with the rainwear community as previously highlighted with my article about Wet & Messy. And also the enjoyment of the slippery material against the skin seems like an obvious shared connection between the sweat and the rainwear community. There are enough people who enjoy the feeling of rainwear against their skin, especially when the gear has a smooth backing like rubber. Thicker PVC rainwear often has a fabric backing but that can be solved by wearing the first layer inside out. A similar experience can be reached by simply wearing a sauna suit which normally is PVC inside and out. Below a suit and picture from PVC-U-LIKE.

Shiny gear
Finally there seems to be a group that is mostly attracted to the overall look of sauna suits on a person they could be attracted to. The main cause of this appreciation for sauna suits would be that the people most likely wearing a sauna suit are professional athletes which tend to be relatively young ( = attractive), relatively athletic ( = attractive), and dedicated to their sport ( = attractive). It is not hard to associate a sauna suit with an attractive athlete who just finishes a training sessions and is now all sweaty and tired and in need for some arms wrapping them to recover and relax. This also links back to the age distribution of people looking for sweaty videos; it are mostly younger viewers who hope to see sporty guys and girls getting sweaty. Below a promotional picture of the British TKO Sport showing one of their modern sauna suits on an attractive model which brings home this point nicely.

Obviously there are companies that still produce and sell rubber sauna suits but their focus is purely on the fetish community. PVC is the better and cheaper option, so don’t expect someone running through the park in an exercise suit from Weathervain, as shown below, anytime soon.

Asking an athlete
How do you think the pleasurable and professional use of a sweat suit differs in experience?
It is probably day and night. Most athletes dread the moment a sauna suit gets involved as it is all but pleasurable. You have to understand that the overall experience of making weight depends largely on the amount of weight you need to lose. Unfortunately the relationship between effort and sweat is not linear: where you sweat a lot at first it starts to slow down when you get dehydrated and it becomes much more unpleasant as well. You move towards a survival mode where the only thing on your mind is water and that is the one thing you cannot have. I hope the pleasurable use of sauna suits does not reach that stage as it can become quite risky and it is not uncommon for athletes to end up at ER when they push it too far.
Do athletes wear any clothes under their sauna suit?
Haha, I would guess most do. They probably wear at least some comfortable clothing underneath, even if it is just to avoid chafing or the suit clinging against your body, and depending on the surrounding temperature you might want to add several warm layers under the suit to sweat quicker as that limits the amount of time you have to wear it.
Any tips for the sauna suit community?
Stay hydrated. For me a sauna suit is linked to competition preparation and suffering, so it will not get me sexually interested, but if it works for you then have fun.
Personal experiences
Out of curiosity, and a longing for the days I had access to a steam room or Finnish sauna, I did try using a rainsuit to mimic the sauna experience. Just a rainsuit would be a very limited effort, so I added a pair of boots, thick rubber gloves, and a gas mask to heat up as much as possible. All that on a summer’s day in the full sun just past noon.
The first thing I noticed is that there is quite a difference in ventilation between a genuine sauna suit and a rainsuit. While a rainsuit might feel hermetically sealed, you quickly notice heat escaping through ventilation vents, the collar, or from the jacket around your waste. While I experimented in just a vintage Agu suit made out of rubberized nylon the first time, I added a second layer of thick PVC the next time to lock in the heat better.

Secondly the gloves and gas masks were the most noticeable elements: without them not much besides some moderate sweating would happen. But with the gloves on I became very aware of the sweat filling up the gloves. And the mask was the most extreme as sweat would start to drip from my face into the mask. Added advantage was the smell of rubber coming from the gas mask and the gloves when they got hot from the sun, which really made it a complete experience.

But was it as good as visiting a regular sauna or steam room? It is not really comparable even though I did experience a much clearer mind after sweating it out in rainwear. The whole sauna experience is normally much more: warming up, cooling down, resting, repeating, eating, etc. It can take a whole day. While here I managed 25 minutes on the first try in one layer and 30 minutes on the second with two layers. And once completely drenched with the sweat sloshing around in my boots I just wanted to sit under the cold shower in my gear hydrating with a bottle of water and a smile on my face.
If you have a comfortable gas mask, thick gloves, and a spot with enough privacy to sit in the sun on a summer day, I would recommend trying it out just to see how you like it because it can certainly be interesting.