A blister is a fluid-filled bump on the skin.
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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
Viral infections, such as
shingles, or herpes
Bacterial infections, such as
Fungal infections, such as
Contact dermatitis, such as
poison ivy, oak, or sumac
- Allergic reactions
- Reactions to certain medications
- Certain cancers
Blistering diseases, such as
Autoimmune disorders, such as
- Insect bites
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
Blisters may cause:
- Fluid-filled bump on the skin, which is often round
- Fluid is usually clear, but may be bloody, cloudy, or purulent
Your doctor will ask you 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.
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:
- 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.
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.
A blister usually heals by itself. See your doctor if:
- The blister is unusually large (for example, bigger than a nickel)
- The blister is in a critical 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
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.
Ramsey ML. Avoiding and treating blisters.
Phys Sportsmed. 1997;25(12).
Last reviewed September 2013 by Michael Woods, MD
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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