Blisters when walking: how to prevent them with boots and socks

Day two of the walk, a little after lunch. A faint prickle at the heel, nothing to worry about, it’ll keep until the next stop. And it does keep, after a fashion: by the next stop there’s a bubble, and every remaining step is counted. The blister is the most ordinary nuisance a walker meets, and one of the easiest to avoid, provided you deal with it before you set off.

A blister comes from repeated rubbing, and heat and moisture help it form [1]. Prevention therefore comes down to four habits: boots in the right size and already broken in, socks that stay dry, protection on the vulnerable spots, and a stop as soon as the skin starts to heat up. This guide expands on that part of the ‘Get your kit together and pack your rucksack’ step in our guide to planning a walk, with what the studies actually measured, and in whom.

Why a blister forms

For the Assurance maladie, France’s national health insurance, a blister is a lifting of the epidermis, the outer layer of the skin, forming a pocket filled with clear fluid. Under repeated rubbing, the epidermis reddens, then separates from the dermis; the blister then protects the wound underneath. Heat and moisture, heavy sweating for example, encourage it to form [1].

US Army researchers, whose recruits walk a great deal under heavy loads, set out the mechanics in a review published in 1995. The greater the friction force, the fewer rubs it takes for a blister to appear. Damp skin rubs more; very dry or very wet skin, less. The sole of the foot, with its thick, tightly held outer layer, is among the most exposed areas, and sustained effort or a heavy load increase the risk [2].

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How your foot presses down matters too. In a small 2010 study of 33 people, those prone to blisters had higher pressures and shear stressesForces that pull the skin parallel to its surface, like a hand sliding across a table and dragging the tablecloth with it. under the sole than the others [3]. And history weighs heavily: among 533 runners surveyed after trail races in France in 2021, those who had had blisters before were far more likely to have them at the finish [4]. If you get them often, this guide concerns you twice over.

Boots in the right size, already shaped to your feet

The first line of defence is the boot. The Assurance maladie asks for footwear suited to the shape of your foot, advises against wearing a new pair for too long, and suggests regularly checking the inside by hand for a split seam or torn leather [5]. The FFRandonnée, France’s hiking federation, calls this the most important point of all [6].

The FFRandonnée’s federation doctor, Dr Catherine Kabani, explains the sizing trap: if the boot is too big, the foot moves and rubs, with blisters at the front of the foot on descents and at the back on climbs. And don’t count on breaking in to rescue a boot that pinches: in her view, it is not the boot that will adapt to your foot [7].

For the rest, trying boots on in the afternoon, choosing a category to suit the terrain and breaking them in before the big day, see our guide to walking boots. One point, though, that may ruffle devotees of the high ankle: for Dr Kabani, the height of the ankle makes no difference to the risk of blisters [7].

Socks: what the studies say

This is the department of received wisdom. Studies do exist, but they are rare, often military, or carried out on runners. Here is what they measured.

Cotton versus acrylic, first. In 1990, a double-blind study had 35 long-distance runners run in two socks identical in every respect except the fibre: the 100% acrylic socks produced fewer blisters, and smaller ones, than the 100% cotton socks [9]. Dr Kabani, for her part, advises against thick cotton socks of the ‘tennis’ type, which encourage sweating, as synthetic materials also do in her view; she prefers lisle in summer, a very fine cotton, fine wool or breathable technical fabrics [7].

Moisture, above all. Among walkers, the material seems to matter less than the water. In 2022, Spanish researchers examined 203 walkers on the Camino de Santiago, on the Camino Francés, after an average of about 250 km on foot: 68.5% had blisters. The proportion of natural or synthetic fibres made no difference, but walking in wet socks multiplied the risk by 1.94. The authors recommend changing socks during long stages [10]. If you’re setting off on the Camino de Santiago, a spare pair weighs less than a blister.

Two pairs or two layers?

The double layer has its fans. Among 357 US Marine Corps recruits in 1996, a thick, dense wool and polypropylene sock, worn over a thin polyester liner sock, brought blisters down to 40% of recruits, against 69% with the standard military sock. The liner on its own, slipped under the standard sock, did not reduce the number of blisters (77%), only the cases serious enough to need treatment [11]. So it was the combination that made the difference, not the second layer as such. So-called anti-blister socks, with a double knit, rest on a similar idea: the two layers rub against each other rather than against your skin, explains Dr Kabani [7].

A systematic review published in 2017 sorted through the evidence: of 11 studies included on socks, antiperspirants and barriers, only 2 deserved moderate confidence. Good-quality evidence is lacking, its authors conclude, and only paper tape may be effective [16]. My view: walking socks that fit you, suited to the activity as the Assurance maladie asks [5], and above all a dry spare pair in the rucksack.

Lacing: locking the heel in place

A heel that rises and falls inside the boot with every step is a blister in the making. Scarpa, which makes walking boots, suggests that heel blisters can come from a boot that holds the heel poorly, and proposes adjusting the lacing, starting from a boot in the right size [17]. Its simplest fix: a surgeon’s knotA simple knot with one extra turn: it holds the tension without slipping. at the bottom of the ankle, before lacing the top. The most secure, the heel lock, takes four steps [17].

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Scarpa presents it as a way of lacing firmly while spreading the pressure rather than concentrating it under a knot, with one drawback: it needs slightly longer laces. Another of the manufacturer’s variations, lacing to the top and then back down, can on the contrary create a pressure point on the ankle [17]. Try it at home, not in the car park at the start.

Dry feet, protected skin, short nails

Keep your feet dry. Blisters develop more easily on damp skin, the Assurance maladie points out, and it advises changing socks twice a day if you sweat a lot [5]. At the lunch stop, taking your boots off for a few minutes and putting on the spare pair costs nothing.

Antiperspirant and powder: mixed results. Among officer cadets at the West Point military academy in 1998, a 20% aluminium chloride solution applied on at least three evenings before a 21 km march cut blisters from 48% to 21%, in 269 people; but 57% of users had irritated skin, against 6% with the placebo [12]. Another antiperspirant, with added emollients, made no difference in 23 men walking in the heat with 21 kg on their backs [13], and the 1995 review found no effect from drying powders [2]. If the idea tempts you, ask a pharmacist for advice, well before you set off.

Prepare your skin. Dr Kabani advises massaging your feet for several days before the walk with a suitable product, to soften and moisturise the skin [7]. The 1995 military review also notes that repeated low-intensity rubbing makes the epidermis thicken, which may reduce the risk [2]: one more reason to put in a few hours’ walking before the big day.

Cut your nails. The Assurance maladie advises cutting them straight across, leaving only 2 to 3 mm beyond the toe, to avoid small injuries and ingrown toenails [8]. A nail too long that knocks against the end of the boot at every step downhill is not something anyone misses.

On the way: stop at the first hot spot

The principle fits in one sentence: you stop as soon as it gets hot. At this hot spotAn area of skin that reddens and burns from rubbing: the first stage of a blister., the FFRandonnée asks you to act as early as possible, with a dressing, at the first burning sensation [6]; Dr Kabani sees it as the first stage of a blister, the redness stage [7]. Waiting for the next stop often means missing the right moment.

The first days count double, at least among the ultramarathon runners studied: in the two paper tape studies, 89% and then 80% of blisters had appeared by day 2, or by the end of stage 2 [14, 15]. On a multi-day walk, keep the dressings within reach from the first morning.

At the first sign of heat, in this order:

1. stop and take your boot off, even if the group is moving on in five minutes;
2. dry the skin and, if your socks are wet, change them [10];
3. put a protective dressing on the area that is turning red [18];
4. run your hand around the inside of the boot: a small stone, a split seam or torn leather is enough to injure you [8];
5. re-lace, holding the heel more firmly if that’s what is rubbing [17].

Dressings belong in the first aid kit on our day walk kit list; add a spare pair of socks.

A blister has formed: basic care

Despite everything, the bubble is there. The NHS says blisters often heal on their own within a week, and that you won’t usually need to see a GP; the steps below are the ones it recommends, which depend on the state of the blister [20].

• Still intact: don’t burst it yourself. Keep it as clean as possible, washing the skin gently and patting it dry, and cover it with a soft plaster or a padded dressing.
• Burst: wash your hands before touching it, let the fluid drain, then cover it with a plaster or dressing. Don’t peel off the skin, and don’t pick at the edges of what remains.
• Large or painful: a GP might burst it with a sterilised needle. A pharmacist can recommend a dressing to cover it while it heals: a hydrocolloid dressing, a moist dressing, protects the blister, helps reduce pain and speeds up healing.

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Until it heals, don’t wear the boots that caused it [20]. Not every health authority says the same about bursting, however: in France, the Assurance maladie considers it useful to drain a large, painful blister that is still intact, using a sterilised needle and keeping the skin that covers it [18]. It puts healing at about 1 to 2 weeks [1], and Dr Kabani also recommends a colloid, or hydrocolloid, dressing [7].

In the end, a blister is won or lost before you set off: boots in your size and already worn, dry socks and a spare pair, a few dressings in the first aid kit. The good habit, after that, is to stop as soon as it gets hot, even when the summit is only twenty minutes away. To dress the rest of you, follow the three-layer system, and for everything else in your preparation, the steps in our guide to planning a walk.

Worth watching

On a bivvy trip in Snowdonia, the Outdoors Magic editor shares his foot-care routine against blisters, including well-fitting boots and an alternative lacing method.

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Guillaume Hoarau

Camping, wild camping, bushcraft and hiking

Guillaume Hoarau writes for Outfarer about camping, wild camping, bushcraft and hiking. A survival-skills enthusiast and a collector of old field manuals, he likes clear explanations, lists that earn their place and other people’s stories, which he tells well.

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