What is a blister?

A blister is a bubble on the skin containing fluid. Blisters are usually circular in shape. The fluid that forms underneath the skin can be bloody or clear.

What causes blisters?

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

  • Burns or scalds
  • Sunburns
  • Friction (from a shoe, for example)
  • Atopic dermatitis
  • Impetigo (a contagious infection of the skin)
  • Pemphigus (a rare, blistering skin disease that often occurs in middle-aged and older adults)
  • Pemphigoid (a blistering autoimmune disorder, more common in older adults)
  • Dermatitis herpetiformis (a blistering autoimmune disorder that usually affects adults between 20 and 60 years old) 
  • Viral infections (including chickenpox and herpes zoster)

What are the symptoms of a blister?

Blisters causes by injury or friction will appear as a localized bubble filled with either clear or bloody liquid. Blisters that are the result of another condition may appear in one area of your body or may be all over your body. Blisters may be painful or itchy. If there is a systemic cause, like an infection, you may also have whole-body symptoms such as fever, pain, or fatigue. The symptoms of a blister may look like other skin conditions. Always see your health care provider for a diagnosis.

How are blisters diagnosed?

Doctors can usually diagnose blisters by looking at your skin.

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.
  • A cold or ice pack may help reduce swelling and discomfort.
  • Keep the area clean and dry. Do not 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 doctor. You may need antibiotics.

Key points

  • 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 resemble 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.

Next steps

Tips to help you get the most from a visit to your health care provider:

  • Before your visit, write down questions you want answered.
  • Bring someone with you to help you ask questions and remember what your provider tells you.
  • At the visit, write down the names of new medicines, treatments, or tests, and any new instructions your provider gives you.
  • If you have a follow-up appointment, write down the date, time, and purpose for that visit.
  • Know how you can contact your provider if you have questions.

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