Cooling underwear for the sauna: how the options actually differ
Short answer: there are four different products being sold under the same idea, and only one of them holds a cold source in position for the length of a sauna session. That is a garment with a dedicated pocket and a frozen gel pack. Everything else is either an insulating pouch with no cold source, a loose pack you have to hold in place yourself, or ordinary cooling fabric that does nothing in a 90 degree room.
This guide names the brands, explains what separates them, and is honest about where our own product sits. We make one of these. We have tried to write the page we wanted to find when we started.
Why is this a category at all?
Because sperm production needs a temperature below core, and a sauna removes the gap. Scrotal temperature in fertile men measures roughly 33 to 35 degrees Celsius against a core of about 37. Roger Mieusset, summarising decades of measurement for an ICNIRP and WHO workshop in 2015, put the risk threshold at above 35 degrees Celsius, with measured depression in count, motility and morphology at 36.
The best measured sauna study is Garolla and colleagues, 2013, in Human Reproduction. Ten healthy men, two fifteen minute sessions a week at 80 to 90 degrees Celsius for three months. Sperm count and motility were strongly impaired at P less than 0.001, and everything returned to baseline six months after the sessions stopped. Read the full breakdown of that study if you want the numbers.
That is the whole demand driver. People do not want to give up the sauna, and they would rather change one variable than quit.
The four form factors
1. Garment with a pocket and a gel pack. A boxer brief or briefs with a sewn in pocket, sold with one or more frozen gel inserts. This is the only design that both removes heat and keeps the cold source in a fixed position while you sit, stand and move. Brands here include KOLDWR, QUOR, Sauna Protocol, SaunaBox, Saun Haus, Health Hercules and, as the original of the form factor going back to around 2014, Snowballs Underwear.
2. Pack and sleeve, no garment. A shaped gel pack in a neoprene or fabric sleeve that you position yourself and wear inside your own underwear. ChillNuts, the Underdog Kit and Kiwi Kooler work this way. Cheaper in principle, and you are not buying sizes, but positioning is on you and it is the part that fails in practice.
3. Insulating pouch, no cold source. A neoprene or silicone cover with nothing frozen in it. The Nut Cooler is the clearest example, and the silicone cups that became briefly popular in Japanese saunas are the same idea. Insulation slows heat transfer, it does not remove heat. In a room 50 degrees above skin temperature, slowing is worth something and is not the same as cooling.
4. Cooling fabric. Moisture wicking or menthol treated underwear marketed as cooling. It works by evaporation, and evaporative cooling is exactly what stops working in hot humid air. Shinesty, who sell a well known cooling boxer, say so themselves in their own copy: their product is for any time except a sauna. Take them at their word.
What to actually look for
Does it hold the cold in position? This is the single question that separates products that work in a sauna from products that work on a sofa. A pack that migrates is a pack that is cooling your thigh. A sewn in pocket sized to the insert is the whole point of buying a garment rather than a bag of ice.
Is there a spare? No frozen gel pack stays frozen indefinitely at 90 degrees Celsius, and any brand telling you otherwise is selling you something. What matters is whether the kit includes a second pack so you can swap between rounds. Most sauna sessions are three or four rounds. One pack does not cover that.
Is the pack shaped, and is it BPA free? A flat rectangular ice pack is uncomfortable and sits badly. Shaped inserts cost more to tool and are worth it.
Is the fabric appropriate for the room? Synthetics behave badly at sauna temperatures and a lot of studios have rules about what you can wear on the bench. Cotton and TENCEL are the common answers.
What does the brand claim? This is a filter, not a feature. Nobody has run a trial of sauna with cooling against sauna without cooling. Anyone quoting you a percentage of fertility protected is extrapolating from studies that were not about their product. A brand willing to tell you what has not been proven is more likely to be honest about the rest.
Who makes what, as of July 2026
Prices move, so treat these as bands rather than quotes, and check before you buy.
Snowballs Underwear is the oldest brand in the form factor, around the sixty dollar mark, and has the most accumulated review history. Notably, their positioning is fertility, vasectomy recovery and varicocele. Sauna is not mentioned anywhere on their site. If you are buying for the sauna specifically, you are adapting a product built for a different job.
QUOR is the closest current analogue to what we make, around forty dollars for the boxer, with an insulated carrier that holds spare inserts and bundle pricing that gets aggressive at three boxers. Their site cites no research at all, which is a stylistic choice rather than a defect, but it is worth noticing.
Sauna Protocol sells briefs with two gel packs at roughly our price point and is frequently sold out. SaunaBox and Health Hercules sit in the same band with cotton briefs and included packs. Saun Haus is the price leader, around thirty dollars, and leads its marketing with a specific percentage figure attributed to a public figure's self experiment, which is not the same thing as a study.
ChillNuts skips the garment entirely and sells a shaped gel pack, a cotton pouch and an insulated case for around forty dollars. If you already own underwear you are happy sitting in, this is a reasonable wedge, and it has a real review history on Amazon.
Cold Pants is not shipping yet but is the most technically interesting thing in the category. They use a phase change material calibrated to hold at a fixed temperature rather than a frozen gel, plus wool felt insulation, and their pitch attacks the plain gel pack design directly. Worth watching.
The Nut Cooler is a neoprene pouch with no cold source, at around twenty five dollars. Cool Beans is a passive airflow design at around sixty. Babystart FertilMate is a menthol hydrogel patch sold through fertility retailers, and is the only product in the wider category attached to a registered randomised controlled trial protocol, published in Trials in 2012. That trial was about nightly use in men with poor semen parameters, not about saunas.
Where KOLDWR sits, including the parts that are not flattering
KOLDWR is a boxer brief with one sewn in front pocket holding one frozen gel pack, and two packs ship in the kit so one is worn and one is in reserve. Forty nine dollars with free US shipping. It is built for the sauna specifically rather than adapted from a fertility or recovery product.
The honest weaknesses: we are at the top of the price band, not the bottom. Saun Haus and SaunaBox undercut us. We are a new brand with a short review history, where Snowballs has a decade of it. And we have not run a laboratory test of pack duration at sauna temperature, so we do not publish a number for it, which is less satisfying than a brand that does publish one.
What we will stand behind: the design solves positioning, the kit includes the spare you actually need for a multi round session, and we do not make a claim the research cannot carry. Peer reviewed work shows sauna heat measurably reduces sperm count and motility and that the effect tracks with cumulative exposure. KOLDWR reduces heat exposure at the place the research points to. We do not claim it improves fertility, sperm count or testosterone.
Common questions
What is the best cooling underwear for the sauna?
For sauna use specifically, a brief with a sewn in pocket and at least two frozen gel packs included, so the cold source stays in position and you can swap between rounds. KOLDWR, QUOR, Sauna Protocol, SaunaBox, Saun Haus and Health Hercules all build to that pattern. Snowballs invented the form factor but does not target sauna use.
Do insulating pouches without ice work?
They slow heat transfer rather than removing heat. In a room fifty degrees above skin temperature that is a partial measure at best, and it will not hold you under the temperature thresholds the research points to.
Can I just bring an ice pack?
You can, and plenty of people do. The complaint that follows is always the same: it slides, it leaks, and it ends up on the bench. A dedicated pocket is the entire difference.
How many gel packs do I need?
At least two. A typical sauna visit is three or four rounds with breaks, and one pack does not cover that. Kits that ship a single insert are underspecified for real use.
Does any of this have clinical proof?
Not for sauna use. There is good evidence that heat impairs sperm parameters, and there is evidence that scrotal cooling improves parameters in men with poor baseline semen quality over eight to twelve weeks of nightly use. There is no trial of sauna with cooling against sauna without cooling. Any brand implying otherwise is going beyond the literature.
Is it uncomfortable?
Cold against warm skin is a sensation you notice for about a minute and then stop noticing. The gel pack sits inside a fabric pocket rather than against bare skin, which is also why it does not cause a cold burn.
Related reading
How to protect your testicles in a sauna
Does scrotal cooling actually work? What the research shows, and what we do not claim
Does sauna lower testosterone? What the research actually says
Sources
Garolla A, Torino M, Sartini B, Cosci I, Patassini C, Carraro U, Foresta C. Seminal and molecular evidence that sauna exposure affects human spermatogenesis. Human Reproduction, 2013, volume 28, issue 4, pages 877 to 885.
Mieusset R. Genital heat stress and semen quality. ICNIRP and WHO International Workshop on Thermal Effects, 2015.
Osman MW, Nikolopoulos I, Haoula Z, Kannamannadiar J, Atiomo W. A study of the effect of the FertilMate scrotum cooling patch on male fertility. SCOP trial, study protocol for a randomised controlled trial. Trials, 2012, volume 13, article 47.
Product details and pricing observed on manufacturer websites in July 2026. Competitor information is provided for comparison and may change without notice.