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What causes running blisters — and how to avoid them

A close-up shot of a runner adjusting their shoes while crouching.
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There's no getting around it — virtually every runner will deal with the pain and discomfort that come with blisters. Fortunately, you can take steps to appropriately treat them and promote fast healing. You can even prevent them from occurring. Here's what you need to know about these pesky pains.

What causes blisters?

Running blisters are caused by a variety of factors. They're most commonly the result of prolonged friction and moisture on your skin, especially if your shoes don't fit properly or you're wearing socks made of material that doesn't best suit the elements in which you run. Increased levels of speed during races and workouts can also be a culprit, along with foot abnormalities such as bunions, hammertoes, and heel spurs. Blisters are especially common in long-distance runners because the longer you're on your feet and experiencing moisture and friction, especially if it's hot and humid outside, the more likely they are to surface.

What do blisters look and feel like?

Running blisters are characterized by small bubbles of skin with clear liquid and sometimes redness or bruising. They can also form under your toenails and bleed if they pop, leaving your toenails looking black. Blisters can sometimes be completely painless or very painful, but the good news is that on their own, they don't pose any serious health risk. However, continuing to run on them can make them more painful, and not caring for them properly could lead to an infection.

Runner on sidewalk

Treatment for running blisters

While you don't have to sideline yourself to heal your blisters, it's important to understand that you should avoid popping most blisters. Doing so can lead to skin trauma or infection. Sometimes, cleaning the area and applying a bandage and antibiotic ointment may be all you need, but if you have a large or extremely painful blister, popping it with a sterilized needle and washing it with soap and water while leaving the skin intact can be the most effective form of relief.

How to prevent them in the first place

Fortunately, painful blisters don't have to be something runners live with as part of the game. To prevent running blisters, make sure you have been fitted properly for the right shoe size and insoles and are wearing quality socks made of technical, dry-fit fabrics instead of cotton. It can also be helpful to lube up your feet with anti-chafe balm and salve before a long and hot run, and tape up any existing blisters with moleskin or a bandage.

By taking these steps, you can make sure you're setting out on the right foot to keep blisters away or at bay for happier training.

Our writer's advice is intended for informational or general educational purposes only. We always encourage you to speak with your physician or healthcare provider before making any adjustments to your running, nutrition, or fitness routines.