On hot summer days, we reach for our coolest, lightest and most breathable clothes to stay as comfortable as we can. But what about what’s underneath your clothes?
If you’re wearing light clothes over underwear, boxer briefs or bras that don’t breathe well, you’ll still be uncomfortably hot and sweaty.
But does “cooling underwear” really exist? Unfortunately not in the sense of that crisp, cool air conditioner feeling, but underwear made with breathable, moisture-wicking fabrics (like Merino wool) can help regulate temperature and keep you cooler in the heat. Some underwear fabrics work far better than others to keep you comfortable.
People tend to hear “wool” and think “warmth,” which is true. But Merino wool underwear is naturally temperature-regulating, so it’s great to wear in both winter and summer. As the old saying goes, two things can be true at the same time. So, how does it actually work?
How underwear can regulate your temperature and keep you cool
Breathability is key for cooling underwear. The last thing you want is for your heat and moisture to stay trapped against your skin. There are ultra-breathable types of underwear out there (like mesh), but you don’t have to go that far for comfort.
Choosing underwear fabrics that breathe well and wick moisture is the most practical way to stay more comfortable. As moisture (sweat) moves away from your skin and evaporates, you’ll feel cooler overall.
Ridge Merino boy shorts: a great cooling option for summer hikes and spontaneous swims.
How Merino wool underwear keeps you cool
Merino wool is naturally temperature-regulating, so it works better than other fibers to keep you warm when it’s cold out and cool when it’s warm out. Its wavy fibers trap air in cold conditions to insulate you and keep you warm, but they also allow heat and moisture vapor to escape when it’s hot.
Wool fibers change shape when wet with water or sweat. Textiles that respond to environmental stimuli like this are sometimes called “smart textiles.” Wool does this naturally, but smart textiles can also be manufactured. When you sweat, wool fibers essentially self-vent so heat and moisture can escape more easily. This study found that thinner wool fabrics (single jersey instead of double knit) do this most effectively.
The other aspect of Merino wool that helps keep you cool is its ability to wick moisture from your skin. In addition to allowing moisture to easily escape, wool moves sweat from your skin to the fabric and then lets it evaporate into the air, so you get an evaporative cooling benefit too.
“If you are planning on camping, hiking or doing any other big outdoor adventures this summer, you need some cooling undies to keep you going. Caldwell says she wears this pair hiking and loves the brand because they are made of high-quality Merino wool. They are also naturally anti-microbial, moisture-wicking, temperature-regulating and odor-resistant.”
- NBC TODAY: “Yes, Cooling Underwear Exists — Experts and Editors Share Their Favorite Options To Beat the Heat”
Ridge underwear can even serve as pool swimwear when the occasion arises.
What about other underwear fabrics for cooling?
Wool is able to absorb about a third of its weight in moisture without feeling wet. Cotton isn’t as good as wool but is far better than synthetics, which can’t hold onto moisture well at all. It sounds counterintuitive to want your underwear fabric to absorb that much moisture, but it’s exactly what you want for cooling.
In a recent study from Australian Wool Innovation Limited, wool was compared to similar polyester, cotton and viscose garments for stop and go sports. Activities where you’re working hard and sweating then returning to rest are particularly hard to manage—this can happen even in daily life in the summer during a workout or when going from extreme heat outside to chilly air conditioning inside.
Wool performed best in a test transitioning from 45% to 80% relative humidity. It was 26% superior to viscose, 45% superior to cotton and 96% superior to polyester. The study also tested human comfort during an activity phase followed by a resting phase, and wool came out on top again.
“Wool base-layer garments deliver significantly better comfort and temperature performance to athletes for an extended resting period. Wool’s ability to diminish after-chill was seen to be long-lasting, showing no sign of disappearing even 25 minutes into a resting phase… While quick-drying fabrics like polyester do lower humidity levels next to the skin, they do not lead to better outcomes for the athlete. The athlete perceives rapid drying during the resting phase as uncomfortable because the rapid evaporation of sweat leads to chilling.”
- AWI’s Angus Ireland
Ridge Boxer Briefs are the key to staying cool on a hot summer camping trip.
Cotton underwear is the most popular, and if you’re used to wearing cotton underwear in the summer, you’ll notice a big difference switching to Merino wool underwear. Cotton tends to feel more wet as it absorbs moisture, and it tends to take longer to dry so you might feel clammy for longer.
You might come across alpaca underwear or, more rarely, cashmere underwear. Both of these natural fibers are better at keeping you warm than cool. While they can wick moisture, alpaca can’t hold as much moisture as Merino wool can, and cashmere tends to retain moisture longer, which can slow down your cooling.
Merino wool is the clear winner for cooling underwear during activity and exercise, but if you’re not moving that much, silk underwear is a good option to consider. While silk isn’t as durable as Merino, it feels cooler to the touch, provides less insulation and allows heat and moisture to escape more easily when you’re at rest.
Another benefit of Merino wool underwear: odor resistance
While not a cooling factor, another major benefit of wearing Merino wool underwear in the heat is the natural odor resistance. When you’re hot and sweaty, smell can quickly become an issue. Merino wool prevents this. There are many other benefits to wearing natural underwear too.
Cooling down in the ocean? Yep, Ridge Boxer Briefs are ready for that too.
Cooling underwear for women
Stay cool in our Merino wool underwear—a full underwear restock is coming this fall.
“Bought my second pair of these for a 7 day backpacking hunt in the wilderness. They stayed cool in the hot weather and freshened up nicely with a dip in some water and a hang dry between trees. I cannot recommend these enough! Phenomenal fit, they don’t ride up when hiking and dry quickly when wet. Perfect for the backcountry.”
- Eryn C., Women’s Ridge Merino Wool Boy Short Underwear“These boy shorts are really comfortable and feel cool in the warm weather! Wool underwear from now on!”
- Cherie M., Women’s Ridge Merino Wool Boy Short Underwear
“They are comfortable, even in hot weather, and don't ride up.”
- Katelyn M. Women’s Ridge Merino Wool Hipster Brief Underwear (pictured above)“Never damp feeling, stays dry even in hot, muggy hiking conditions. Line dries fast. Have over a dozen wool thongs now, and these are my preference because they are low rise.”
- Bethany S., Women’s Ridge Merino Wool Thong Underwear
For cooling bras, try our Women’s Send-It Seamless Merino Wool Sports Bra or our Women’s Merino Wool Bralette.
Our bralette works equally well for hot summer days as it does as a cold weather next-to-skin layer.
Cooling underwear for men
Keep cool and avoid chafing in our Men’s Ridge Merino Wool Boxer Briefs (reviews below) in regular length or long. If you prefer a brief, we have those too. All of our underwear will be restocked this fall.
“Just purchased these a week ago and have been wearing them in hot weather with lots of walking...and man do these underwear deliver! Keeps things cool and dry down there and are very comfortable. They also never smell and hang dry quickly after a wash.” - Dontae B.
“I live in Phoenix AZ, and hike here year round. Why would someone from the desert wear wool? Cool comfort is why. Wool passes moisture when it's made right, doesn't chafe, and when on the trail, washes easily with my wool blend socks in Woolite. These fit and wear the best.” - Ragnar B.
“As for dealing with perspiration during activity, cotton gets soggy and stays wet, synthetics do better but are clammy when wet, but these you hardly notice against your skin, maybe it's because they dry so fast. 100% recommended, you won’t be disappointed.” - Mike J.
Ridge boy short underwear and boxer briefs in a limited edition tie-dye for summer.
