Part UT Health San Antonio

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, which can occur with wearing a tight-fitting shoe or gripping a tool
  • Second-degree burns
  • Infections
  • Contact dermatitis, such as poison ivy, oak, or sumac
  • Insect bites
  • Allergic reactions
  • Reactions to certain medications or chemicals
  • Certain cancers
  • Blistering diseases, such as, epidermolysis bullosa, porphyria, or pemphigus
  • Autoimmune disorders
  • 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

Symptoms

Blisters may cause:

  • Fluid-filled bump on the skin, which is often round
  • Fluid is usually clear, but may be bloody, cloudy, or contain 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
  • There are many blisters
  • 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 a blister:

  • 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.
  • Avoid skin contact with irritating chemicals
RESOURCES:

American Academy of Dermatology
https://www.aad.org

National Institute of Arthritis and Musculoskeletal and Skin Diseases
https://www.niams.nih.gov

CANADIAN RESOURCES:

Canadian Dermatology Association
https://dermatology.ca

Health Canada
http://www.canada.ca

REFERENCES:

Blistering skin conditions. DermNet New Zealand website. Available at: https://www.dermnetnz.org/topics/blistering-skin-conditions. Updated September 2015. Accessed August 17, 2017.

Blisters. Better Health Channel website. Available at: https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/blisters. Updated April 2016. Accessed August 17, 2017.

Blisters—causes. NHS Choices website. Available at: http://www.nhs.uk/Conditions/Blisters/Pages/Causes.aspx. Updated March 23, 2015. Accessed August 17, 2017.

Blisters, calluses, and corns. Kids Health—Nemours Foundation website. Available at: http://kidshealth.org/en/kids/blisters.html. Updated February 2015. Accessed August 17, 2017.

Last reviewed September 2018 by EBSCO Medical Review Board Michael Woods, MD, FAAP  Last Updated: 9/3/2014