Blisters are the classic long-day killer. You can have the fitness, the pack dialled and the weather on your side, and a hot spot on one heel at hour three can still turn a great day into a limp home. The good news: blisters are largely preventable, and one of the oldest fixes in the book is a small tuft of wool. Here's how blisters actually form, and how to stop them.
The short version
- Blisters come from friction and shear on damp skin, repeated over time. Same recipe as chafing, just on your feet.
- Keep your feet dry. Wet skin blisters far more easily, so ditch cotton socks for merino.
- Take the friction off your hot spots. A little wool over the spot, or a base layer of anti-chafe gel, stops your skin taking the drag.
- Get your footwear right. The correct size, a foot-shaped toe box and a locked-down heel prevent most blisters before they start.
- Already got a hot spot? Stop and deal with it there and then, not at the car.
What actually causes a blister
A blister is your skin's response to shear: the top layers get dragged back and forth over the layers beneath until they separate and the gap fills with fluid. Three things drive it, and they stack. Friction from your sock and shoe. Moisture, because damp skin grips and tears far more easily than dry skin. And time, because it's the repetition over hours that does the damage.
Moisture is the big lever. In a 2025 systematic review of friction injuries in athletes, hikers in wet socks had 1.94 times the risk of foot blisters compared with dry (Islam and Islam, 2025), and the same review found that swapping cotton for moisture-moving socks cut new blisters substantially. Keeping your feet dry is genuinely half the battle.
Keep your feet dry
Cotton socks soak up sweat and hold it against your skin, which is the worst thing you can do. Merino is the answer: it moves moisture off your skin and keeps working when it's damp. On multi-day trips, a dry spare pair to change into partway through a big day is one of the best blister tools you can carry.
Take the friction off your hot spots
This is where wool earns its place. Everyone has spots that rub, usually heels, the back of the toes, or the side of a big toe. Tease off a small amount of Blister Stop Wool, wrap it lightly over the spot, and pull your sock on over the top. Your sock now slides against the wool instead of dragging on your skin, and the wool wicks sweat away from the exact place a blister would start. Ours is unbleached lamb's wool infused with mānuka oil, which is naturally antibacterial and antifungal and gives the wool a light, pleasant scent, no small thing a few days into a trip when feet and socks get ripe. Unlike a plaster it won't peel off when your foot gets sweaty, and you can add a bit more on the trail the moment something niggles.
For broader areas that rub, or as a base under the wool, our Anti-Chafe Gel is worth a spot in the pack too. It reduces friction, repels moisture and lets skin breathe, rather than sealing sweat in the way Vaseline does, which leaves skin soft and more blister-prone (we've compared the two here). It's 100% natural and washes out of your socks. Gel on the skin, wool over the worst spots, is a hard combination to beat.
Get your footwear right
More blisters trace back to shoes than to anything else, so this is worth getting right.
Size for the end of the day, not the start. Feet swell over long distances and in the heat, and they slide forward on descents. You want roughly a thumb's width in front of your longest toe so they aren't jammed into the front going downhill. Try shoes on later in the day when your feet are already a little swollen, and with the socks you'll actually hike in.
Choose a foot-shaped toe box. A tapered toe box squeezes your toes together, which is exactly how you get blisters between and on top of them. Look for a shoe shaped like a foot, with room for your toes to spread. Brands like Topo Athletic and Altra are built around this idea, but the feature matters more than the label: stand on the insole and check your toes aren't wider than it is.
Lock the heel. A heel that lifts with every step saws at your skin and is the classic cause of heel blisters. You want the heel held firmly while the toes stay free. A heel-lock (runner's loop) lacing technique, using the spare eyelets at the top, pulls the heel back into the shoe and stops the slide.
Use your laces to fix pressure points. Laces aren't all-or-nothing. If you get a hot spot over the top of your foot or a high arch, skip that eyelet or use window lacing to take the pressure off just there. A surgeon's knot lets you lock tension in one zone and leave another looser. And re-check tension on the trail: snug them before a long descent, ease them if your feet swell.
Keep grit out. A single bit of sand or a seed in your sock will chew a blister faster than anything. Shake your shoes out at breaks, and on gravelly or sandy trails a pair of low gaiters keeps debris out in the first place.
And give new shoes time. Skin adapts to load, so build your distance up rather than jumping straight into a big day in fresh boots.
More than blisters
Wool isn't only for hot spots. It's brilliant for padding, so if you've got a callus, a bony bit or a pressure point that aches on long days, a little wool over it is genuinely cushy and takes the edge off. And if your toes overlap or crowd each other, a small piece woven between them keeps them apart, stops the toe-on-toe rubbing, and heads off the blisters that form in those tight gaps. A tin lives easily in a first-aid kit or hip belt pocket.
If a blister has already started
The moment you feel a hot spot, stop and deal with it. Ignoring it for another kilometre is how a niggle becomes a burst blister. Clean the area, dry it, and put wool or a dressing over it to take the friction off. If a blister has already formed and the roof is intact, it's usually best left unbroken as a natural barrier, just protected from further rubbing. If it's torn open, keep it clean and covered. If the skin around it becomes increasingly red, swollen, warm or painful over the following days, see a health professional, as that can point to infection.
The bottom line
Blisters aren't bad luck, they're friction and moisture and time, and all three are things you can manage. Keep your feet dry in merino, take the friction off your hot spots with a bit of wool and a base of anti-chafe gel, and get your footwear right. Do that and the long days stop ending with a limp.
This article is general information, not medical advice. If a foot problem is getting worse rather than better, see a health professional.
Sources
- Islam R, Islam KN. Cutaneous Friction Injuries and Blister Prevention in Athletes: From Stratum Corneum Mechanics to Smart-Textile Solutions: A Systematic Review. Premier Journal of Sports Science, 2025.
- Gerhardt LC et al. Influence of epidermal hydration on the friction of human skin against textiles. Journal of the Royal Society Interface, 2008;5(28):1317.