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 a blister?

Blisters are caused by injury, allergic reactions, or infections, which may include the following:

  • Burns or scalds

  • Sunburns

  • Friction (from a shoe, for example)

  • Eczema (also known as atopic dermatitis)

  • Impetigo. A contagious infection of the skin.

  • Pemphigus. A rare, blistering skin disease often occurring in middle-aged and elderly adults.

  • Pemphigoid. A blistering autoimmune disorder, more common in older adults. 

  • Dermatitis herpetiformis. A blistering autoimmune disorder usually affecting adults between 20 and 60 years old. 

  • Viral infections (including chickenpox and herpes zoster)

The symptoms of a blister may resemble other skin conditions. Always consult your doctor for a diagnosis.

First aid for blisters

Blisters often heal spontaneously. 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 an adhesive bandage or dressing on the area to keep it clean.

  • Observe 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. Antibiotics may be needed.

Treatment for blisters

A blister will usually heal on its own. Treatment may include:

  • Keeping the area clean

  • Covering an unbroken blister with a loose bandage 

  • Antibiotics (to treat infections)

  • Dressings on burst blisters