Definition

A blister is a fluid-filled bump on the skin.

Blisters

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Causes

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, including sunburn or frostbite
  • Viral infections, such as chickenpox , shingles , or herpes
  • Bacterial infections, such as impetigo
  • Fungal infections, such as athlete’s foot
  • Contact dermatitis, such as poison ivy, oak, or sumac
  • Allergic reactions
  • Reactions to certain medications
  • Certain cancers
  • Blistering diseases, such as porphyria
  • Autoimmune disorders, such as pemphigus
  • Insect bites
  • Scabies
  • Risk Factors

    Factors that increase your chance of getting blisters include:

        
  • Wearing ill-fitting shoes
  • Repetitive work with hand tools
  • Getting a sunburn or frostbite
  • Severe skin swelling, especially of the legs
  • Symptoms

    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
  • Diagnosis

    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.

    Treatment

    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
  • Prevention

    To help reduce your chance of getting blisters, take these steps:

        
  • Wear shoes that fit properly.
  • Always wear socks with your shoes.
  • Wear sports socks when exercising or participating in sports.
  • Use gloves or protective padding when working with tools.
  • Wear a hat, protective clothing, and sunscreen when out in the sun.
  • Wear sandals in public showers to protect your feet from athlete's foot.
  • Wear long shirts and pants when working outside to protect yourself from poison ivy.