Blisters

What is a blister?

A blister is a bubble on the skin containing fluid. Blisters are often shaped like a circle. The fluid that forms below the skin can be bloody or clear.

What causes blisters?

Injury, allergic reactions, immune diseases, or infections can cause blisters. These include:

  • Burns or scalds
  • Sunburns
  • Rubbing (friction), such as from shoes rubbing against the skin
  • Atopic dermatitis
  • A contagious skin infection (impetigo)
  • Allergic reactions such as poison ivy
  • A rare, blistering skin disease that often occurs in middle-aged and older adults (pemphigus)
  • A blistering autoimmune disorder that is more common in older adults (pemphigoid)
  • A blistering autoimmune disorder linked to gluten sensitivity that often first appears in adults between ages 30 and 50 (dermatitis herpetiformis)
  • Viral infections such as chickenpox and herpes zoster

What are the symptoms of a blister?

Blisters caused by injury or rubbing (friction) will appear in that one area as a bubble filled with either clear or bloody liquid. Blisters that are due to another condition may appear in one area of your body. Or they may be all over your body. Blisters may be painful or itchy. In some cases the blister may be caused by something that affects the whole body, such as an infection. Then you may also have whole-body symptoms such as fever, pain, or extreme tiredness (fatigue). The symptoms of a blister may look like other skin conditions. Always see your healthcare provider for a diagnosis.

How are blisters diagnosed?

Healthcare providers can often diagnose blisters by looking at your skin. If your provider thinks you may have an infection or a skin disorder, a blister biopsy may be done. A piece of the blister is removed and checked under a microscope. Or a skin culture may be needed.

How are blisters treated?

Blisters often heal on their own without treatment.  If needed, treatment will vary, depending on the cause. Some general guidelines for first aid may include:

  • Wash the area with soap and water.
  • Apply a cold or ice pack which may help reduce swelling and discomfort.
  • Keep the area clean and dry. Don't burst or puncture the blister.
  • If the blister bursts, place a bandage or dressing on the area to keep it clean.
  • Watch the area for signs of infection such as increased warmth, swelling, redness, drainage, pus formation, or pain. If you notice any signs of infection, call your healthcare provider. You may need antibiotics.

Key points about blisters

  • A blister is a bubble on the skin containing fluid.
  • Blisters are caused by injury, allergic reactions, or infections.
  • The symptoms of a blister may look like other skin conditions.
  • If you have whole-body symptoms, such as a fever, talk with your healthcare provider.
  • Blisters often heal on their own.
  • It is important to keep the area clean and dry.
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