A blister is a fluid-filled bump on the skin.
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Blisters have many different causes. These may include:
  • Friction or constant pressure, such as from wearing a tight-fitting shoe or gripping a tool
  • Second-degree burns
  • Infections
  • Contact dermatitis, such as poison ivy, oak, or sumac
  • Allergic reactions
  • Reactions to certain medications
  • Certain cancers
  • Blistering diseases, such as porphyria
  • Autoimmune disorders
  • Insect bites
  • Scabies

Risk Factors

Factors that may increase your chance of blisters include:
  • Wearing ill-fitting shoes
  • Repetitive work with hand tools
  • Getting a sunburn or frostbite
  • Severe skin swelling, especially of the legs


Blisters may cause:
  • Fluid-filled bump on the skin, which is often round
  • Fluid is usually clear, but may be bloody, cloudy, or containing pus


You will be asked about your symptoms and medical history. A physical exam will be done. Blisters may be diagnosed on appearance. The cause can be determined by the activity you were doing when the blisters appeared.


A blister will often heal without treatment. You may need treatment for a condition that is causing the blisters.Some general tips for treatment include:

Protect the Area

  • Be gentle with the injured area. To prevent further injury, use a bandage made for blisters. Also, put a cushion around the blister to protect it. The blister should begin to shrink in about seven days.
  • Do not pop or lance the blister. Opening the blister increases the chance of infection and delays healing.
  • Do not scratch any blisters. If it is infectious, scratching may spread the infection. It also puts others at risk for getting the infection. Try over-the-counter medication that is applied to the skin to relieve any itching or discomfort. If you still have problems with the blisters, call your doctor.

Wash the Area

If the blister is closed, gently wash the area with soap and water. Apply a bandage to protect it.If the blister is open, gently wash the area, apply an antibiotic ointment, and then cover it with a sterile dressing or bandage.

See Your Doctor If:

A blister usually heals by itself. See your doctor if:
  • The blister is unusually large—bigger than a nickel
  • The blister is in a sensitive area, such as on the face or the groin
  • The blister is associated with a burn
  • There are signs of infection, such as increasing redness around the blister, red streaks, severe swelling, pus drainage, fever, or an increase in pain

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