Cold Pants are the world's first thermally-insulated organic undergarment engineered for saunas. Like a wearable thermos, our design shields cooling elements from 90°C air—so you can enjoy the heat without worrying about your fertility.
Your testes evolved to sit outside your body for a reason: sperm production requires temperatures 2–4°C below core body temperature. In a sauna at 80–100°C, your body's natural cooling mechanisms are completely overwhelmed. Studies show regular sauna use significantly decreases sperm count—effects that take 3–6 months to reverse.
Unlike standard underwear with cooling packs that melt in minutes, our wool-felt thermal barrier shields the cooling element from the hot air—while a conductive inner layer draws heat away from your body.
The base garment is certified organic cotton—no synthetic fibers releasing chemicals when heated. Wool insulation is natural, breathable, and maintains its insulating properties even when damp.
Our cooling packs use Phase Change Material calibrated to 18°C—cold enough to protect your fertility, warm enough to prevent discomfort. Lasts significantly longer than ice in extreme heat.
Your body has built-in cooling for your testes: the cremaster muscle adjusts position, the dartos muscle changes surface area, and a network of veins pre-cools incoming blood. But at 90°C, these systems fail completely. Heat floods in from all directions—the hot air, radiant heat from the sauna stones, even the bench you're sitting on.
Cold Pants solve this with a simple principle: insulate from the outside, conduct from the inside. A thermal barrier (wool felt or aerogel) blocks the 90°C sauna air from warming the cooling pack, while the skin-facing layer efficiently transfers heat away from your body. The result: your cooling pack lasts the full session, not just the first five minutes.
That's a 108°C temperature difference
Standard cooling packs melt in under 8 minutes. Cold Pants are designed to last.
Not just a pocket—a contoured cup shape that wraps underneath, protecting from heat in all directions including the bench below.
Soft, flexible, and safe at high temperatures. Won't degrade in the sauna. Feels premium against a moisture-wicking mesh barrier.
Unlike ice packs that can cause cryoburn on hot, wet skin, our 18°C Phase Change Material is calibrated for safety and comfort.
Strong elastic supports the weight of the cooling pack without sagging. Boxer brief style covers inner thighs for additional insulation.
Ice packs in regular underwear? They melt in under 8 minutes at 90°C. The cotton acts as a heat bridge, not a barrier. You end up with a warm, wet mess—and no protection.
Cold Pants are engineered from the ground up for extreme heat environments
From research to reality—Cold Pants launches summer 2026
Join our wait list for early thermal test results, pre-order access, and product updates. We'll share the data as we develop Cold Pants—no hype, just science.
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Safety: Designed for heat protection. Do not apply frozen elements directly to bare skin. Discontinue use if discomfort occurs. Cold Pants is not a medical device.