A blister is a bubble of fluid under the outer layer of skin. The fluid may be clear or filled with blood or pus.
What is the cause?
There are many possible causes of blisters, including a burn, disease, an allergic reaction, or rubbing of your skin against something. Blisters caused by your skin rubbing against something, like tools that you are using or shoes that donâ€™t fit well, are called friction blisters. Friction blisters usually happen when you start a new sport, exercise program, or sport season; when you wear new shoes; or when the weather is hot and humid.
What are the symptoms?
When the skin gets irritated, fluid collects under the outer layer of skin. This can be painful. The surrounding area may be red, sore, or swollen. Blisters can be very small or quite large.
Most blisters are filled with clear fluid. If the fluid in a friction blister is bloody, it usually means that a lot of force caused the blister.
If a blister is filled with pus, it may be infected. Infected blisters are very painful. They may be swollen and feel warm to the touch. You may even have a fever.
How is it diagnosed?
Your healthcare provider will examine you and ask about your symptoms, activities, and medical history.
How is it treated?
Itâ€™s best to leave most small blisters alone. Keep them clean and covered with an antibiotic ointment and a bandage. Put a little petroleum jelly around the blister or the part of a shoe that causes the irritation so there is less rubbing. If possible, donâ€™t wear the shoes that caused the blister. Wear heavier socks, if possible, to cushion the blister. Wear gloves if the blisters are on your hands.
You can buy moleskin at a drugstore to protect the blister. Cut a round piece of moleskin that is bigger than the blister and cut a hole in the center. Then put the moleskin on your skin with the hole over the blister. Cover the moleskin with a bandage.
Blisters usually drain by themselves and last about 3 to 7 days. The skin covering the blister helps protect you from an infection. Leave it in place until it is very dry and the underlying skin has become tough and painless. Then you can trim off the layer of dry skin with a clean pair of scissors.
Large blisters may need to be drained with a sterile needle. Talk to your healthcare provider about this.
If a blister gets infected, you need to see your healthcare provider. Your provider may prescribe an antibiotic for the infection.
Contact your provider if you have new or worsening symptoms.
How can I help prevent blisters?
Follow these guidelines to have less rubbing of your skin:
Make sure that your shoes fit well.
Don’t wear wet shoes.
Wear 2 pairs of socks to protect your feet.
Wear gloves to protect your hands.
Put petroleum jelly (Vaseline) on spots that tend to rub, or use a foot powder.
Put athletic tape or a bandage over sore spots.
Developed by RelayHealth.
Adult Advisor 2015.1 published by RelayHealth. Last modified: 2012-09-26 Last reviewed: 2014-01-23
This content is reviewed periodically and is subject to change as new health information becomes available. The information is intended to inform and educate and is not a replacement for medical evaluation, advice, diagnosis or treatment by a healthcare professional.
Blister from Friction: References
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Micheli, Lyle J. and Mark Jenkins, The Sports Medicine Bible: Prevent, Detect, and Treat Your Sports Injuries Through the Latest Medical Techniques, HarperCollins, 1995.
Oâ€™Connor, Francis G, et al. ACSMâ€™s Sports Medicine A Comprehensive Review. Wolters Kluwer/Lippincott Williams & Wilkins, 2013.
Sarwark, John. Essentials of Musculoskeletal Care, 4th ed., American Academy of Orthopaedic Surgeons, 2010.