How to Prevent Blisters When Running Long Distances and Marathons

The short answer

To prevent blisters when running, cut down friction and moisture at the spots that rub. Wear running shoes that fit, neither too tight nor too loose, and break new pairs in gradually. Wear moisture-wicking running socks instead of cotton, and change them if your feet sweat heavily. Before long runs, put a lubricant or a protective covering on the spots that have blistered before. And deal with a hot spot as soon as you feel it rather than running through it. That is the core advice from the NHS and the American Academy of Dermatology.

What nobody can offer is a guarantee. A 2017 systematic review in Wilderness & Environmental Medicine looked at sock, antiperspirant and barrier strategies across running, hiking and marching and found a "paucity of high-quality evidence" for any of them. So treat everything below as ways to improve your odds, and test each one on training runs before you rely on it in a race. This page is general information, not medical advice; if you have a foot condition, diabetes or a blister that looks infected, see the health note at the end.

Why blisters show up on long runs

A friction blister forms when rubbing forces separate layers of the outer skin and fluid fills the gap. In a review in Sports Medicine, Knapik and colleagues explain that two things determine the chance of one forming: the size of the friction force and the number of times it cycles across the skin. The higher the friction, the fewer cycles it takes. Moist skin increases friction, blisters are more likely where the skin's outer layer is thick and held tightly to what's beneath it, as on the soles of the feet, and more vigorous activity appears to raise the odds.

Put that next to a training plan and the pattern is obvious. Every extra mile adds strides, and every extra minute adds sweat inside the shoe. A 2014 blister trial in the same journal opens by noting that friction blisters occur in up to 39% of marathoners. Here's how the longest run grows across the published beginner plans, and where to put your attention at each level:

One more reason to build gradually: Knapik's review notes that recent exposure to repeated, low-intensity friction leads to changes in the skin, including thickening of the outer layer, which may reduce the likelihood of blisters. A plan that adds distance a little at a time gives your feet that chance.

The prevention checklist

1. Shoes that fit. The AAD says shoes shouldn't be too tight or too loose; the NHS says properly fitted, comfortable shoes. Fit changes with the socks you wear, so try shoes on in your running socks; our guide to what size running shoes to get walks through it.
2. Break new shoes in gradually. The NHS advises breaking in new footwear with short periods of wear. For a runner, that means the first runs in a new pair are short ones, never a long run or a race. If you're replacing a worn-out pair before a race, do it weeks ahead, not days.
3. Moisture-wicking socks, not cotton. The AAD recommends nylon or moisture-wicking socks, and the NHS thick, moisture-wicking sports socks. In a double-blind study of 35 long-distance runners, acrylic socks were associated with fewer and smaller blisters than otherwise identical cotton ones.
4. Change wet socks. The NHS suggests changing socks frequently if your feet sweat a lot. On a long run in heat, that can mean a dry pair stashed at the halfway point of a loop.
5. Try two pairs if one isn't working. The AAD suggests two pairs if one doesn't help. Knapik's review reports that a thin polyester sock under a thick wool or polypropylene sock reduced blisters in Marine recruits. Two socks change how your shoe fits, so try it on a short run first.
6. Reduce friction on known hot spots. The AAD suggests powder or petroleum jelly on problem areas, and sports-medicine reviews by Ramsey and Bergeron both list lubricants among prevention measures. Anti-chafe sticks do the same job without the grease; Body Glide lists "feet and heels in athletic shoes" among the places to use its original stick.
7. Cover spots that always blister. The AAD suggests adhesive moleskin or soft bandages on vulnerable spots, secured well so they don't slide.
8. Stop at the first hot spot. The AAD's advice is to stop your activity if you feel pain or discomfort or your skin turns red. On a 20-miler, a minute spent on a hot spot at mile 6 beats running the last 14 miles on a blister.

What the research can and can't show

The advice above is consistent across medical sources, but the trials behind specific products are thin. Here's what the studies we read actually found:

• Sock fiber: the acrylic-versus-cotton trial above is the clearest runner-specific result. Knapik's review summarizes it as acrylic socks resulting in fewer foot blisters in runners. The running socks we recommend are nylon, polyester, olefin and merino blends rather than pure acrylic; the takeaway that holds up is "not cotton."
• Powders and antiperspirants: Knapik's review reports that antiperspirants with emollients and drying powders applied to the foot do not appear to decrease the probability of friction blisters. The AAD still lists powder as an option for problem areas, so this is one where the evidence and the everyday advice don't fully line up.
• Tape: in a randomized trial in multi-day ultramarathons, runners had paper tape applied to one foot and the other left bare. Tape showed no significant protective effect, though 84% said they'd choose it again. The 2017 review still concluded, with moderate confidence, that paper tape may be an effective barrier. Mixed, in other words.
• The overall picture: the 2017 review screened 806 articles, included 11 studies and rated only 2 as moderate confidence. Clinical and method differences were too large to pool the results.

The practical upshot: combine the basics, test them on training runs, and be skeptical of any product that promises blister-proof feet. None of the picks below makes that promise here; they're designed to reduce friction and moisture, which is what the research points to.

Socks and balm: what to look for

Since friction and moisture are the causes, a blister-conscious sock should have a non-cotton fiber, a seamless toe so no ridge crosses the top of your toes, and a heel tab or deep heel pocket so the sock can't slide down into the shoe. It should be sized to your foot on the maker's chart, since a sock that bunches creates the ridges you're trying to avoid. If your blisters form between the toes, a toe sock is the design aimed at that spot. For a lubricant, look for one that goes on dry and stays on through sweat, in a size you can carry.

Our full ranking of seven running socks, including merino and hot-weather options, is in the best running socks. Body Glide also sells a separate foot-specific stick, Foot Glide, which we haven't reviewed here.

A long-run and race-day routine

Before you go

Start with clean, dry feet and the socks you've already worn on long runs. Put a thin layer of lubricant or anti-chafe stick on the spots that have rubbed before, such as heels or toes, and cover any spot that always blisters with moleskin or a soft bandage, as the AAD suggests. If your heel lifts noticeably in the shoe as you walk, revisit the fit or the lacing before the long run, not during it.

During the run

Stop at the first sign of a hot spot. On half and marathon long runs, a pocket-size stick and a couple of bandages take up almost no room in a belt or vest, and they let you deal with a hot spot at mile 8 instead of running on it until mile 16. If your socks are soaked through on a hot day, the NHS advice to change sweaty socks applies mid-run too.

After the run

Take your shoes and socks off, let your feet dry and look at them. A red patch that didn't blister today tells you where to put the balm next time. If you have diabetes, the CDC advises checking your feet every day, including for blisters.

Race day

Nothing new. Race in the shoes, socks and balm you used on your last long runs, and pack the same pocket stick and bandages. Our marathon gear checklist and half marathon gear checklist cover the rest of the race-morning kit.

If you get a blister anyway

The NHS advice is not to burst a blister yourself. Keep it clean by gently washing and patting it dry, and cover it with a soft plaster or padded dressing; a pharmacist can recommend hydrocolloid dressings, which the NHS says protect the blister, reduce pain and speed healing. If it bursts, let the fluid drain before covering it, and don't peel off the loose skin. The NHS also advises not using whatever caused the blister until it heals: for a runner, that's the shoe or sock that rubbed.

The AAD also advises against popping or draining, with one exception: a blister that is large and very painful may need draining. Its method is to sterilize a small needle with rubbing alcohol, pierce one edge of the blister, let the fluid drain, wash the area with soap and water, apply petroleum jelly and leave the "roof" of skin in place to protect the raw skin underneath. The AAD says most blisters heal on their own in one to two weeks.