Published on March 8, 2024 at 8:00 / Updated on March 26, 2024 at 8:00

A blister, also known as a bulla or phlyctena, is a sac of clear fluid that forms under the skin.


Friction (ex. wearing shoes that are too big), burns and stings can all cause blisters.


  • Sac filled with clear fluid
  • Pain
  • Redness


When a blister is intact and located in an area where it is not at risk of bursting, it is important to protect it, since the intact skin acts as a natural barrier against bacteria and reduces the risk of infection. To do so, cover with a sterile bandage. The blister will reabsorb and heal on its own.

If the blister is intact but is located in an area where it is likely to break, it is advisable to drain it. The first step to draining a blister involves cleaning the area with soap and water. Then, using a needle that has been sterilized with alcohol, perforate the base of the blister. Using a gauze pad, gently apply pressure on the blister to drain the fluid. Lastly, cover the empty blister with a sterile bandage. Some bandages are specially formulated for use on blisters - they absorb the fluid, promote healing and reduce pain.

It should be noted that once a blister has been drained, the excess skin should not be removed as it increases the risk of infection. Simply clean the skin and cover it with a sterile bandage.

You should see a doctor if:

  • There are signs of infection (redness, heat, swelling, pus, persistent pain and fever)
  • The blisters are the result of a burn that is either extensive, located on the face, involves a child or is affecting the use of the limb on which they are located (antibiotic therapy and proper bandaging may be required)


Preventing blisters is quite simple. Protect any area that is prone to repeated rubbing by wearing gloves, socks, bandages or other protective devices. You can also purchase specially designed sports socks and cushioned insoles. In addition to wearing properly fitted shoes, it is important to remember that different sports activities call for specific footwear.

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