Merino wool comes from a particular variety of sheep that produces extra fine and soft wool. In the outdoor world, it is commonly used in socks and long underwear, among other uses. A natural fiber, it is warm and comfortable against the skin and a popular alternative to synthetic options like polyester or polypropylene.
Overall, Merino wool is a delightful material that I recommend for certain products, but definitely not others, especially given the premium you will pay for it over other options. Here’s why I love it, and how it has also let me down.
Over the years I have used Merino wool extensively in socks, long underwear, and men’s briefs. I have found it to be extremely comfortable, soft, warm, and a delight to wear. Like all wool, it has the remarkable property of being able to absorb a fair amount of moisture while still providing ample insulation and warmth. It readily sucks up body moisture without feeling damp, a bonus on your feet (the second sweatiest part of your body after your armpits) or any next-to-skin application like a base layer or briefs.
Merino wool can also provide a delightful—and delightfully soft—cushion underfoot, something you can appreciate whether you’re wearing Smartwool expedition-weight socks (my personal favorite) or a Northeast-made special from Darn Tough Socks.
I particularly like my men’s Merino wool base layer top from Smartwool, which is fashionable enough to double as a comfy and warm long-sleeve shirt for me during the cool months of fall and spring. Indeed, I’m wearing a Merino top right now as I write this. Merino wool good!
This delightful material has one fatal flaw, however. Durability. Or, more accurately, a lack thereof. For any application where there is regular friction against the wool, it just doesn’t hold up over time. It wears out like clockwork.
Case in point: Smartwool Men’s boxer briefs. I’ve been wearing these for years. Despite the price tag—$45 for a pair of underwear!—their incredible comfort and form-fit has swayed me to invest in quite a few pairs. The only problem? Somewhere between 18 and 24 months of regular use, they develop small, then gaping, holes in the butt, just from the friction of everyday sitting and use.
That’s a pretty short shelf life in my book, especially since I have multiple pairs of synthetic fabric boxers and briefs that are still functional (holes free!) after more than a decade of use.
I’ve seen similar wear in my Smartwool expedition socks, though the wear-out of the wool is somewhat mitigated by the more durable nylon mesh that underpins the sock structure. Clearly, though, without a more durable fiber underpinning it, the wool just doesn’t hold up. That’s probably why Smartwool has introduced ‘Core Spun’ technology into its latest version of briefs, which wraps Merino fibers around a nylon core thread. The long-term durability of this latest technology has yet to play out (I have a couple pairs of boxer briefs with this tech and will report back), I’ve been turned off enough to try an alternative (Ex Officio’s Give-N-Go sport mesh 9″ boxer briefs, which are less expensive at $32 and so far have been outstanding).
Bottom line for me is this. Merino wool is great stuff—unless it’s being used in a high-friction location, where you may want to consider alternatives.