6 Best Odor Resistant Underwear For Multi Day Treks That Stay Fresh for Days

You’re on day three of a trek through the Cascades, the air is crisp, and the views are epic. But as you hoist your pack after a break, you catch a whiff of something decidedly… unfresh. Good gear can make or break a trip, and what you’re wearing underneath it all matters more than you think.

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Why Odor-Resistant Underwear is a Trail Essential

When you’re packing for a multi-day trip, every ounce counts. The old logic of "one pair per day" simply doesn’t fly when you’re carrying everything on your back. The goal is to bring just two or three pairs: one to wear, one to dry, and maybe a spare for camp.

This system only works with performance underwear designed to resist the bacteria that cause odor. Unlike cotton, which traps moisture and becomes a breeding ground for funk, technical fabrics (both merino and synthetic) pull sweat away from your skin and dry quickly. This not only keeps you more comfortable and reduces chafing, but it dramatically extends how long a single pair can be worn before needing a wash.

On a long, humid slog through the Appalachian Trail, this means less swampiness and a major boost to morale. In the dry, dusty canyons of Utah, it means less grit and irritation. Ultimately, investing in a few good pairs is about carrying less weight, staying more hygienic, and being a more pleasant tent-mate.

ExOfficio Give-N-Go 2.0: The Classic Trail Staple

If you’ve ever asked a seasoned backpacker for an underwear recommendation, you’ve probably heard of ExOfficio. The Give-N-Go line has been a trail favorite for decades, and for good reason. They are the quintessential synthetic workhorse: durable, breathable, and incredibly fast-drying.

Made from a lightweight mesh nylon, these boxers can be washed in a stream and be practically dry by the time you’ve set up your tent. The fabric is treated with an antimicrobial finish to keep odor at bay for days on end. While they may not have the luxurious feel of merino wool, their ruggedness and reliability are hard to beat, especially on extended trips where durability is paramount.

The fit is functional and non-restrictive, making them a solid choice for everything from a weekend trip to a full thru-hike. They represent a fantastic balance of performance and price, making them one of the most accessible and dependable options for any adventurer.

Icebreaker Anatomica: Premium Merino Wool Comfort

For those who prioritize next-to-skin comfort above all else, merino wool is the answer, and Icebreaker’s Anatomica line is a prime example. These boxers are made with a core-spun fabric, where merino fibers are wrapped around a nylon core. This gives you the incredible softness, temperature regulation, and natural odor resistance of wool, with a boost in durability.

Merino wool is almost magical in its ability to stay fresh. The fibers naturally inhibit bacterial growth, meaning you can wear these for multiple days of hard hiking without them developing a serious funk. They also regulate temperature brilliantly, keeping you comfortable in a wider range of conditions than most synthetics.

The main tradeoff is drying time. While they handle moisture well while you’re wearing them, they take longer to air dry after a wash compared to a synthetic pair like the ExOfficio. They also come at a premium price, but for many, the unparalleled comfort on a long, cold day in the Rockies makes it a worthwhile investment.

Smartwool Merino 150: All-Season Wool Performance

Smartwool is another giant in the world of merino, and their Merino 150 boxer briefs are a direct competitor for the most versatile trail underwear. The "150" refers to the fabric weight (150 g/m²), which hits a sweet spot for four-season use. It’s light enough for summer heat but has enough substance to provide a bit of warmth on a chilly morning.

Like other merino options, the Merino 150 excels at odor control and comfort. The wool feels great against the skin and wicks moisture effectively during high-exertion climbs. Smartwool’s construction often features smooth, flatlock seams to minimize chafing under a heavy pack’s hip belt, a small detail that makes a huge difference by day four.

Choosing between Smartwool and Icebreaker often comes down to personal preference in fit and feel. The Smartwool 150 is a fantastic all-arounder that proves its worth whether you’re sweating on a desert trail or layering up for a mountain ascent. It’s a reliable piece of gear that you put on and forget about, which is the highest praise any underwear can receive.

Saxx Quest Boxer Brief: Unbeatable Pouch Support

Long days on the trail involve repetitive motion that can lead to serious discomfort and chafing. Saxx addresses this head-on with their innovative BallPark Pouch™, a 3D hammock-shaped pouch that keeps everything in place. For many hikers, this design is a complete game-changer, eliminating the need for constant readjustment and preventing skin-on-skin friction.

The Quest model is specifically designed for travel and adventure. It’s made from a pin-dot mesh synthetic fabric that is extremely lightweight, moisture-wicking, and quick to dry. It combines the support of a unique design with the high-performance attributes needed for multi-day use, including an anti-odor treatment.

While the pouch design is the main draw, the overall construction is top-notch, with flat seams and a comfortable, non-binding waistband. If chafing has been your nemesis on past trips, or you simply value a more supportive fit during long descents, the Saxx Quest is an option you absolutely must consider.

Arc’teryx Motus SL Boxer: Ultralight & Fast-Drying

For the fast-and-light crowd or anyone hiking in sweltering heat, the Arc’teryx Motus SL (Superlight) Boxer is engineered for maximum performance. This is minimalist gear at its finest. The Phasic™ FL fabric is incredibly thin, ridiculously lightweight, and dries faster than almost anything else on the market.

These are built for high-output activities. The material actively pulls moisture from your skin and disperses it for rapid evaporation, keeping you as dry as possible during grueling uphill climbs. The trim fit and gusseted crotch are designed for unrestricted movement, making them ideal for trail running, fastpacking, or any adventure where every gram and every second counts.

The tradeoff for this ultralight performance is a bit of durability and a less luxurious feel than merino. However, when the primary mission is to stay dry and move fast, the Motus SL is in a class of its own. It’s a specialized tool for demanding conditions.

Patagonia Essential Boxer Briefs: Recycled Comfort

Patagonia brings its commitment to sustainability to the forefront with the Essential Boxer Briefs. Made with a significant percentage of recycled materials and sewn in a Fair Trade Certified™ factory, this is a choice you can feel good about. But this isn’t just about ethics; the performance is right up there with the best.

These boxers use a moisture-wicking synthetic fabric that feels exceptionally soft and stretchy, offering all-day comfort. They feature a comfortable, stay-put waistband and functional fly, making them a practical choice for daily wear and trail life. An anti-odor treatment ensures they can handle multiple days of use before needing a rinse.

The Patagonia Essentials strike a great balance. They aren’t the absolute lightest or the absolute warmest, but they are supremely comfortable, perform reliably, and are built with a conscience. For the hiker who wants a do-it-all piece of gear from a responsible brand, these are an excellent pick.

Merino vs. Synthetic: Choosing Your Trail Underwear

The biggest decision you’ll make is the material. There is no single "best" fabric; the right choice depends on your priorities, the climate you’ll be in, and your budget. Understanding the core differences is key.

Synthetics (nylon, polyester) are the champions of durability and drying speed. They can take a beating on a long thru-hike and will dry in a flash after a quick wash in a creek. However, even with antimicrobial treatments, they will eventually develop an odor faster than wool.

• Synthetic Pros: Extremely durable, very fast-drying, often more affordable.
• Synthetic Cons: Can feel clammy, less natural odor control over the long term.
• Best For: Hot and humid climates (like the Southeast), trips where you’ll be washing gear frequently, budget-conscious hikers.

Merino wool is the king of comfort and natural odor resistance. It feels softer, breathes better, and can be worn for an astonishingly long time before it smells. It also insulates when wet, a critical feature in cold, damp environments. The downsides are a higher price tag, less long-term durability, and a slower drying time.

• Merino Wool Pros: Superior odor resistance, excellent temperature regulation (warm when cool, cool when warm), very comfortable.
• Merino Wool Cons: Less durable, slower to dry, more expensive.
• Best For: Cold weather, dry climates, trips where comfort is the top priority and you can’t wash gear often.

Ultimately, the best system for many long-distance hikers is a mix of both. Start the trip with two pairs of merino and one synthetic. Use the merino for most days and save the fast-drying synthetic pair for rainy stretches or for wearing right after a wash.

Don’t let analysis paralysis keep you off the trail. Any of these options will be a massive upgrade from your everyday cotton underwear. Pick one that fits your budget and planned adventures, then get out there and put it to the test, because the best gear is the gear that gets you outside.