Why You Keep Getting Blisters (and How to Stop Them)

A blister can turn a good run, a long hike, or a day in brand-new shoes into a miserable limp home. It starts as a warm, tender spot on your heel or toe, and by the time you take your shoe off, a fluid-filled bubble has already formed. Most blisters are minor, but they are also almost entirely preventable, which makes getting them again and again especially frustrating. Once you understand what is happening under your skin, the fixes are simple and cheap.

What a blister really is

A friction blister forms when skin is repeatedly rubbed in the same spot. The rubbing separates the top layer of skin from the layers beneath it, and the gap fills with clear fluid called serum. That fluid is your body cushioning and protecting the damaged tissue underneath while it heals.

Three ingredients make blisters more likely: friction, heat, and moisture. That is why blisters peak during summer runs, long hikes, and the first weeks in new shoes. Sweaty feet soften the skin, and a shoe that slips slightly at the heel grinds the same spot with every stride. Cotton socks make it worse because they soak up sweat and stay damp against the skin.

Blisters most often appear on the heels, the balls of the feet, and the sides of the big and little toes. Blisters from burns, frostbite, or skin conditions are different problems, so this guide focuses on the friction kind.

Why some people get them constantly

If you get blisters over and over, one of a few usual suspects is almost always to blame.

The first is fit. Shoes that are too big let your foot slide around inside, and shoes that are too small pinch and rub. A well-fitting shoe should hold your heel in place with no slipping, while leaving about a thumb's width of space between your longest toe and the end of the shoe. Feet also swell during long walks and runs, especially in heat, so shoes that feel perfect in the store can feel tight by mile five.

The second is socks. Thick cotton socks are the classic blister-maker. Switch to moisture-wicking socks made from synthetic blends or merino wool, which pull sweat away from the skin. If you are prone to blisters, try a thin liner sock under a slightly thicker outer pair. The two layers rub against each other instead of against your skin.

The third is doing too much, too soon. Breaking in new shoes on a 10-mile hike, or jumping from a 3-mile run to a 10-mile run in a weekend, gives your skin no time to toughen up. Skin adapts to friction gradually. Big jumps in distance or brand-new footwear skip that adaptation entirely.

Foot shape matters too. Bunions, flat feet, and high arches create pressure points where a shoe rubs harder, and an insole or a different shoe shape may fix a blister that always appears in the same spot.

How to treat a blister safely

Most small, intact blisters heal best if you leave them alone. The skin over the blister is a natural bandage that keeps bacteria out, so resist the urge to pop it. Cover it with a clean bandage or blister pad, and change it daily or whenever it gets wet or dirty.

If a blister is large, very painful, or in a spot where it will burst on its own anyway, the American Academy of Dermatology advises that careful draining is reasonable. Wash your hands and the area with soap and water, sterilize a clean needle with rubbing alcohol, and make a small puncture at the edge of the blister. Gently press out the fluid, but leave the overlying skin in place. Then apply petroleum jelly, cover it with a nonstick bandage, and change the bandage daily.

Do not peel off dead skin, and do not apply alcohol, hydrogen peroxide, or iodine directly to an open blister. They irritate healing tissue. Plain petroleum jelly and a clean covering do the job better.

Do not drain a dark red blood blister yourself. Cover it, avoid more pressure on it, and see a clinician if it is very painful.

Stop a blister before it forms: the hot spot trick

The single most useful blister skill is learning to act on a "hot spot." That warm, red, slightly stinging patch is a blister in its earliest stage, before the skin has separated. If you deal with it right then, you can often prevent a blister entirely.

Carry a small kit on long outings: bandages, athletic tape or moleskin, and petroleum jelly. When you feel a hot spot, stop and dry the area, then place a donut-shaped piece of moleskin around it so the tender area sits in the hole, and tape it in place.

A dab of petroleum jelly on areas that tend to rub also reduces friction, a favorite trick among marathon runners. Taping known trouble spots before you start, with tape smoothed flat so it has no wrinkles, can prevent the problem entirely.

Prevention that actually works

The best prevention plan is boring, and that is why it works. Start with shoes that fit and break them in gradually. Wear new shoes for short walks around the neighborhood before taking them on a long outing, and never debut a new pair on race day or the first day of a hiking trip.

Choose moisture-wicking socks and change them if they get soaked. On very long hikes, carrying a spare pair and swapping them halfway through can prevent a blister at mile eight.

Try heel-lock lacing: thread the laces through the top eyelets to form loops, then cross them through those loops before tying. It keeps your heel from slipping and fixes heel blisters for many runners.

Build up distance gradually, by no more than about 10 percent per week, so your skin and muscles adapt together.

When to get medical care

Most friction blisters heal within a week, but some need a clinician. Get care promptly if you see spreading redness, increasing pain, warmth, pus, red streaks, or a fever, because those can signal infection. Also seek care if a blister is very large, extremely painful, or does not improve after a week.

People with diabetes, poor circulation, or nerve damage in the feet should be especially careful. A small foot wound can become serious when healing is slow or when you cannot feel pain normally. If you have diabetes, do not try to drain a blister yourself, and contact your clinician or podiatrist for any foot blister that breaks open, looks infected, or will not heal.

The same applies to blisters that keep coming back in the exact same spot despite good shoes and socks. A podiatrist can check for foot structure problems, recommend insoles, and rule out skin conditions that can look like friction blisters.

The bottom line

Blisters feel like bad luck, but they are usually a fit, friction, or moisture problem with a practical fix. Leave small blisters covered and alone, act fast on hot spots, wear moisture-wicking socks, break in shoes slowly, and tape the spots you know are trouble.