Stay Fresh and Dry: Why We Prefer Merino Wool Next to Our Skin

This deep-dive is sponsored by Chosenwoven, a sustainable brand that creates comfortable and cute underwear sets out of merino wool and plant-based Tencel. 

Wearing traditional wool can be a challenge, even on a cold winter’s day. We all have memories of suffering through the holidays in our itchy sweaters. So to suggest wearing close-fitting woolen activewear during a sweaty workout or as undies next to your most sensitive parts? Unthinkable.

And yet, many brands are starting to release active woolen wear, including sports bras, socks, base layers, leggings, and even underwear. That’s right: merino wool has been gaining popularity as the best ‘next-to-skin’ fabric. 

Companies like Chosenwoven are opting for wool for reasons other than avoiding synthetic microfiber pollution. They believe that, done right, woolen clothing can be more comfortable, sweatproof, and odor-resistant than its synthetic competition, while being the clear eco-friendly choice. 

Polyester, the dominant outdoor and athletic material and the most widely used fiber in the world, is made from fossil fuels, can cause skin sensitization, and doesn’t biodegrade.

You may be a skeptic, but stick with us — by the end of this post, you’ll be ready to jump into the latest sexy wool undies. 

Synthetic Fabrics Can Be Itchier Than Merino Wool

Counter to popular belief, you’re more likely to get ‘textile dermatitis’ from synthetic materials. 

Stewart Collie, PhD, the science team leader for bioproduct and fibre technology at AgResearch (a New Zealand Crown Research Institute lab), set out to test people’s reactions to polyester and wool. The sixteen volunteers spent the day wearing close-fitting base-layer shirts made from merino wool with a polyester patch on their back. The early data indicated that the wool area supported healthy skin, while the polyester patch had a drying effect with some inflammation. 

How could that be? Well, synthetic fabrics are not as breathable as wool, making us sweat more. And textile dermatitis from synthetics is more likely to occur after a workout.

Synthetic fabrics also make use of ‘disperse dyes’. Disperse dyes are synthetic dye compounds used specifically for dyeing synthetic materials such as polyester and nylon and have been shown to be chemical sensitizers, meaning they irritate many people when exposed repeatedly. This is especially true of the dyes used to make black and blue fabric, which just so happens to be an extremely popular color of choice for activewear. These dyes are also more likely to be released when we sweat, making them very poor choices for activewear. All of this is to say that these dyes are the most prevalent cause of all textile-related allergic contact dermatitis.

Lynn M. Fowler, BSN, RN, has studied how wool affected dermatitis. “Pure wool, when dyed, holds the color tightly and little is able to be released from the wool. Dye can cause allergies when used on clothing that is a mixture [of] synthetic materials, as they are not generally color fast.”

Plus, polyester microfibers not only end up in the local waterways, they break off into your house dust, where you can breathe them in. And whatever is in those microfibers, such as BPA, can end up in your body. 

Meanwhile, wool has a reputation for itchiness for two reasons; it can cause an allergic reaction in a minority of people, and it can cause a physical itch in others.

Evidence suggests that wool allergies have increased between 2004 to 2015. This reaction is caused by your immune system working overtime when coming into contact with wool, specifically lanolin, the waxy substance sheep produce to weatherproof their wool. However, despite the increase, less than 2% of people tested for wool allergy as of 2015 had a legitimate contact allergy to lanolin. 

For most of us, we experience irritant contact dermatitis. And it turns out it’s dependent on the thickness of the wool fibers. Garments made from thicker yarns in the range of 30 to 32 microns, which stimulate your pruriceptors, or, ‘itch detectors’. Meanwhile, the Merino sheep, which originated in Spain and is a popular breed in Australia, New Zealand, and South Africa, produces wool fiber with a naturally lower micron count of 18.9, well below the itch threshold of 30 microns.

“There will always be the odd individual who is more sensitive than others,” Dr. Stewart Collie says. “We all vary in [the] extent to which we have that sensitivity. Once you get below a threshold—probably around 17, 18-micron fiber diameter, it’s likely to be comfortable for everyone.”

Merino Wool Is Healthier for Your Skin

Merino wool is also naturally odor-resistant due to the fiber’s unique properties. This odor control happens because wool can absorb large amounts of water, unlike hydrophobic synthetics. The absorption capabilities of wool are twice as much as standard cotton, and a staggering thirty times more than polyester.

By absorbing the moisture away from the skin, wool discourages bacterial growth. The makeup of wool fibers allows the fabric to lock this moisture away, releasing this moisture (and the odor) when we wash our clothes. This characteristic of wool means that we don’t need to wash our garments after every wear. Hanging your merino clothes on a hanger overnight to air out can keep them fresh.

Wool also helps with temperature regulation by helping you stay warm while remaining breathable, making it perfect for winter sports and summer hikes. 

Wool is also naturally elastic. This means wool exercise clothing can stretch with us while we work out — without the use of plastics like elastane. This elasticity also means wool keeps its shape long-term, making it an excellent investment for your exercise needs. 

Wool Is a Zero-Waste Product

Merino wool base layers are naturally a zero-waste product from beginning to end. Unlike cotton, which has to be cut and leads to a lot of factory off-cuts going to the landfill, knitting merino wool clothing is a no-waste process.

At the end of a merino wool garment’s life, it can easily be recycled into insulation or blankets. In fact, 100% wool garments are some of the few clothing that is actually recycled today. Garments (like underwear and leggings) that have added synthetics like elastane are extremely difficult to recycle and often end up in landfills. 

But what about if your merino wool undies do end up in the ocean for some reason? It should still be okay. Studies have repeatedly shown that synthetic materials, which are made of plastic polymers, take many hundreds of years to break down in the environment, releasing microfibers along the way, which get washed into local waterways—and your drinking water. 

Wool has no such issue. 

In another study, Dr. Collie compared the biodegradation of standard household fibers in a marine environment and found that treated wool degraded one one-third slower than cellulose pulp (the mushy stuff that is made into Tencel, lyocell, and similar fabrics). Meanwhile, synthetic materials (nylon, polyester, and polypropylene) degraded up to 10 times slower. In fact, nylon degraded at 0.8% of the rate of cellulose pulp. 

“Polyester, nylon, [and] polypropylene didn’t biodegrade, whereas the wool materials did. They were well on the way to full biodegradation by the completion of that test,” Dr. Collie says.  

It’s important to base our decisions upon hard science, but it’s also common sense.

“The reality is that we know that fur from animals, fiber from sheep, and feathers from birds … don’t stay in the environment forever because otherwise, over the millions of years in which life has been on the planet, we’d be piled high in the material,” Dr. Collie says. “And that’s clearly not the case. So we know that nature runs a circular system.”

In Stewart’s study, they also tested untreated wool against ‘machine washable wool’, which was treated with a crosslinked polyamide. Surprisingly, this polyamide contributed to an increased rate of degradation in a marine environment. It was hypothesized the treatment may have led to a reduction in the wool’s cuticle, leaving it vulnerable to microbial decay not found in your regular washing cycle. 

Regardless, both types of wool tested degraded when exposed to the marine environment and at a far more rapid rate than any of the polymer-based fabrics tested. 

How To Wash and Care for Merino Wool Clothing

It’s surprisingly easy to take care of most merino wool garments. 

Check the garment’s care tag suggestions as each item and manufacturer differ. Machine washable wool will have a note on the garment tag saying so. You can turn your wool garments inside out when washing them, and use a gentle cycle with cold water and a mild and natural detergent. Lay them flat to dry afterwards. Though in Chosenwoven’s case, you can tumble dry your undies on low if you’re short on time or space!