Running Blisters


Blisters are fluid-filled sacks on the surface of the skin caused by burns, friction, colds, allergies, drug reactions, or infections. The body responds by producing fluid, which builds up beneath the part of the skin that is afflicted, causing pressure and pain. A blood blister occurs when the friction ruptures tiny blood vessels.

Blisters on feet

For our purposes, blisters are most often caused by friction when shoes or socks rub against your skin. Anything that intensifies friction and rubbing can start a blister including:

  • Faster pace running
  • Longer distance running
  • Hot weather running
  • Poor-fitting shoes
  • Ill-equipped socks

Blisters can be caused by foot abnormalities like:

  • Bunions
  • Heel spurs
  • Hammertoes

Friction blister

Heat and moisture intensify friction by making your feet swell and exacerbate the blister problem. This explains why many runners only suffer blisters during races, especially marathons. You’re perspiring more, running longer and faster, and these combinations are the recipe for blister-making.


While most blisters don’t pose a serious health risk, they should be treated with respect. A painful blister can sideline a runner, but more importantly, a blister can also get infected. Serious infections can result when one uses a dirty needle to pop a blister.

Symptoms of blisters

blister is a bubble of skin filled with clear fluid. It can range in size from pinpoint size to more than an inch in diameter. Blisters are different than pustules, which contain thicker, yellow-white material called pus.

If the cause is a long-distance training run in the heat, blisters may manifest as skin redness, or itching in the afflicted area. There may also be pain in the blister area.

Treatment of blisters

Blisters caused by running are typically pretty benign. There are a couple of schools of thought when it comes to treating blisters. They answer the question, should I pop it or not?

The first, is from the American Academy of Dermatology Association. They recommend the following:

“If you do get a blister, be patient and try to leave it alone. Most blisters heal on their own in one to two weeks. Don’t resume the activity that caused your blister until it’s healed.

To treat a blister, dermatologists recommend the following:

  1. Cover the blister. Loosely cover the blister with a bandage. Bring in the sides of the bandage so that the middle of the bandage is a little raised.
  2. Use padding. To protect blisters in pressure areas, such as the bottom of your feet, use padding. Cut the padding into a donut shape with a hole in the middle and place it around the blister. Then, cover the blister and padding with a bandage.
  3. Avoid popping or draining a blister, as this could lead to infection. However, if your blister is large and very painful, it may be necessary to drain the blister to reduce discomfort. To do this, sterilize a small needle using rubbing alcohol. Then, use the needle to carefully pierce one edge of the blister, which will allow some of the fluid to drain.
  4. Keep the area clean and covered. Once your blister has drained, wash the area with soap and water and apply petroleum jelly. Do not remove the “roof” of the blister, as this will protect the raw skin underneath as it heals.

As your blister heals, watch for signs of an infection. If you notice any redness, pus, or increased pain or swelling, make an appointment to see your doctor or a board-certified dermatologist.”

Popping blisters

The other school of thought is a little less alarmist. If you have a large blister, and you feel you need to drain it, WebMD says to do the following:

  • Use a sterilized needle (to sterilize it, put the point or edge in a flame until it is red hot, or rinse it in alcohol).
  • Wash your hands and the area thoroughly, then make a small hole; the fluid will drain on its own.
  • If the fluid is white or yellow, the blister may be infected and needs medical attention.
  • Do not remove the skin over a broken blister. The new skin underneath needs this protective cover.
  • Apply an antibiotic ointment or cream.
  • Look for signs of infection to develop, including pus drainage, red or warm skin surrounding the blister, or red streaks leading away from the blister.

Blister infection

The skin acts as a protective covering over a sterile environment. Furthermore, if the fluid amount is small and you try to pop it, you could cause additional problems by making it bleed. Leave small blood blisters intact, also. Otherwise, you risk getting bacteria into your bloodstream.

When a blister breaks open, germs can enter the wound and cause a skin infection. Blisters may break open if they encounter continued friction or if someone pops or drains the blister.

According to, symptoms that indicate the infection of a blister include:

  • worsening redness around the blister, although this may not be apparent in people with darker skin
  • pain that gets worse rather than better over time
  • swelling that gets worse rather than better over time
  • the fluid becoming cloudy or resembling pus
  • yellowish crusting on the area
  • tenderness in the area

If a blister does become infected, you will need to speak to a doctor. Physicians will prescribe antibiotic tablets or a topical ointment or cream to help the body fight the bacteria that are causing the infection.

Blister on toe

This is a small exception but may afflict some chubby runners. A blister under a nail is best treated by a professional. You never want to deliberately remove the toenail.

Prevention of blisters

  • Moisten your feet. Just like sweaty skin, dry skin is also more prone to friction.
  • Use skin creams and lotions daily to maintain moisture.
  • Use blister-free socks.
  • Slather your feet with Vaseline or another lubricant before you run.
  • Wear two pairs of socks so the friction occurs between the two socks, rather than between the sock and skin.
  • Wear shoes and socks that fit your foot properly.

Other tips

For proper shoe and sock fit. There should be a thumb width of space between the toes and the end of the toe box. Your socks should fit smoothly, with no extra fabric on the toes or heels.

Shoes that are too small will cause blisters under the toes and on the ends of the toenails.

Socks with reinforced heels and toes also help reduce friction.

Synthetic socks wick moisture away from the skin. Cotton may be lighter, but it retains fluid.

Use Second Skin, a padded tape that stays on even when wet. It can help form a protective shield between your skin and sock, preventing blisters.