We make boxer shorts for women, one of the five options below, so read this accordingly. We have tried to be straight about where merino beats us, which is most of the time on a multi-day trek. Specifications checked against each brand's own site in August 2026.
The short version
For a multi-day trek, merino wins. It dries fastest, resists odour naturally, and you can wear a pair for days. Icebreaker and Smartwool are the brands to look at.
For a long day walk where thighs rub, merino loses on one thing: nobody makes it with a long leg. Every merino option here is a brief, a bikini or a hipster, all of which stop well short of where thighs actually touch.
That is the trade this whole article is about. Best fibre, or enough coverage. You rarely get both.
The five options, compared
| Fabric | Longest leg | Dry speed | Odour resistance | Returns once worn | |
|---|---|---|---|---|---|
| Icebreaker | Merino wool | Hipkini, short | Fastest | Excellent, natural | Standard policy |
| Smartwool | Merino and lyocell | Bikini, short | Very fast | Excellent | Standard policy |
| Runderwear | 92% recycled polyamide, 8% elastane | 8 inch long boxer | Very fast | Poorer, synthetic | None once worn |
| Flissie | 95% bamboo viscose, 5% elastane | 6 or 9 inch | Moderate | Not claimed | 60 days, free swap on whole first order |
| Boody | Bamboo viscose, seamfree | Boyleg, short | Moderate | Not claimed | 30 day comfort guarantee |
1. Icebreaker, for multi-day trekking
Merino wool, and the Merino 150 Siren Hipkini recorded the fastest dry time in CleverHiker's side-by-side testing. Merino's real advantage on a multi-day trip is odour resistance: you can wear a pair for several days in a way you cannot with anything else here.
The limitation is coverage. Icebreaker's women's range is briefs, hipsters and bikinis. If your thighs rub, none of them reach far enough down to stop it.
2. Smartwool, the same trade with a softer hand
Merino blended with lyocell, which adds softness and helps with odour resistance. CleverHiker put the Everyday Bikini among the fastest drying they tested.
Same limitation. Bikini cut, so no thigh coverage. Priced at the higher end.
3. Runderwear, the technical long leg
92% recycled polyamide with 8% elastane, 360 degree seamless construction, flatlock edging, and silicone grippers around the leg hems to stop them travelling. The women's long boxer has an 8 inch inseam, which is genuinely long enough to stop thighs rubbing.
If you walk fast, sweat hard or run the descents, this is the technically strongest long-leg option here.
Two things to weigh. Synthetics hold odour more than merino or cellulose fibres, which matters over several days. And Runderwear do not accept returns on underwear once it has been worn, which is a real risk on something you cannot try on first.
4. Flissie, the longest leg
95% Tanboocel bamboo viscose with 5% elastane, in a 6 or 9 inch leg, UK 8 to 30 at one price, dyed to OEKO-TEX Standard 100.
Bamboo viscose breathes well and moves moisture rather than holding it, so it feels cooler than a synthetic on a warm climb. It does not dry as fast as merino or polyamide, which is why we would not pick it for a multi-day trip where you are washing in a stream.
For a long day out, a coast path, a hill walk or 20,000 steps in a city, a long leg is the thing that stops the day being ruined by chafing: the 6 inch covers the top of the inner thigh, where most rubbing starts, and the 9 inch reaches just above the knee.
Today I've been on an 11 mile hike in the Peak District and I didn't have to fuss with them once. They never rolled up under my trousers and the waistband was unnoticeable.
Phillippa, UK, verified review
I use them for hiking in particular, they are great for sports activities and general wear too.
Gemma, UK, verified review
5. Boody, the budget bamboo option
Bamboo viscose, genuinely seamfree rather than flat-seamed, OEKO-TEX certified, B Corp, and sizes up to 4XL. A 30 day comfort guarantee.
The limitation for hiking is the same as the merino brands. Their longest women's style is a boyleg, which is short. Comfortable, but it will not solve chafing on a long walk.
What actually matters on a long day
Leg length, if your thighs touch. This is not a small factor, it is the difference between finishing comfortably and limping the last two miles. Anything stopping between 2 and 4 inches down the thigh does not reach.
Dry speed, if you are out for more than a day. On a single day walk it barely matters. On a multi-day trip where you rinse a pair each night, it is the whole game, and merino wins.
Odour resistance, for the same reason. Merino genuinely outperforms everything else here. Synthetics are the worst of the group.
Seams and waistband. A pack hipbelt sits exactly where most waistbands sit. A wide flat band is better than narrow elastic under a loaded belt, and flat or bonded seams beat overlocked ones.
What does not matter as much as brands suggest: antibacterial claims. REI's own guidance on hiking underwear is worth reading here, because it says plainly that boxer styles add coverage that can prevent chafing but are prone to bunching. That is a fit and sizing problem, not a fabric one.
Cotton, and why every hiking guide tells you not to
Cotton absorbs sweat and holds onto it. On a hill in changeable weather that is genuinely uncomfortable and, in cold conditions, a real problem, because wet fabric against skin pulls heat away from you.
The old advice that cotton kills is overstated for a summer stroll. For anything remote, long or cold, it is sound.
Sizing, which is where most people go wrong
Underwear that is too small is the most common cause of bunching and riding up on a walk, whichever brand you buy. A tighter leg has to stretch further and grips less evenly.
If you are between sizes, go up. If you are choosing between two lengths, the 6 inch is where most people start.
Being a size 16-18, horse riding 5/6 days a week, walking more than 18,000 steps a day. Soft, super comfortable, stretchy, breathable and ZERO CHAFFING. Just ordered 5 more.
A.R., UK, verified review
So what should you actually buy?
| Your trip | Buy |
|---|---|
| Multi-day trek, washing as you go | Merino. Icebreaker or Smartwool |
| Long day walk, thighs rub | A long leg. Ours at 6 or 9 inch, or Runderwear at 8 inch |
| Fast hiking, hill running, heavy sweat | Runderwear. Technical synthetic dries fastest |
| Warm weather day walking | Bamboo viscose. Cooler against the skin than synthetic |
| Cold or remote | Merino, and definitely not cotton |
| Tight budget | Boody, or any non-cotton pair you already own |
If you are only buying one pair and you chafe, buy the longest leg you can find. Fibre is the second question.
See ours here. 60 day comfort guarantee, free swap on your whole first order, free UK delivery.
Questions
What is the best underwear for hiking?
For multi-day trekking, merino wool from Icebreaker or Smartwool, because it dries fastest and resists odour naturally. For a long day walk where thighs rub, a long-leg option from Runderwear or us, because no merino brand makes one.
Is merino wool underwear worth it for hiking?
For multi-day trips, yes. It dries quickly and you can wear a pair for several days without it smelling, which matters when you are carrying everything. For a single day walk the advantage is much smaller and the price is much higher.
Can you wear cotton underwear hiking?
For a short summer walk, it is fine. For anything long, cold or remote, no. Cotton absorbs sweat and holds it, which is uncomfortable at best and pulls heat away from you in cold conditions.
What underwear stops chafing when walking?
A leg long enough to reach where your thighs actually touch, which usually means 6 inches or more. Fabric affects how it feels, but leg length decides whether it works at all.
Does hiking underwear need to be seamless?
It helps, particularly under a pack hipbelt where the waistband is compressed. Flat, bonded or seamfree edges are all better than overlocked seams. It matters less than leg length if your problem is chafing.
How many pairs should I take on a multi-day hike?
Two or three, and rinse as you go. This is the main practical reason merino is worth the money on longer trips: it dries overnight and does not hold odour, so two pairs go further than three of anything else.
What underwear is best under walking trousers?
Something with a flat waistband that does not sit exactly where your trouser waistband or hipbelt sits, and a leg long enough that nothing rides up over several hours. Both problems get worse with distance rather than better.
