A collection of fluid beneath the surface of the skin

  • Age, gender, genetics, and lifestyle are not significant factors

A blister forms when fluid leaks from blood vessels in the skin, usually after minor injury, and collects to form a small, raised area just beneath the outer layer of skin. The most common causes of single blisters are friction, such as that caused by a badly fitting shoe, and burns, including sunburn. Wide-spread blistering may be caused by eczema, or it may occur in some viral infections, such as chickenpox and shingles (see Herpes zoster). The bacterial skin infection impetigo may cause pus-filled blisters. There are also a number of much less common but potentially life-threatening conditions that result in blistering either on specific areas of skin or over the whole of the body (see Blistering diseases).

Blistering caused by minor damage usually heals rapidly without treatment. New skin develops beneath the blister, the fluid is gradually absorbed, and the top layer of skin dries and peels away. If the skin is broken, or if the blistered site is likely to be damaged further, you should protect the area with a dry, sterile dressing. Blistering due to disease or infection may need drug treatment.

You should not prick a blister to release the fluid because the skin acts as a barrier against infection. If the blisters are filled with pus or you notice spreading redness in the surrounding skin, consult your doctor.

From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.

The subjects, conditions and treatments covered in this encyclopaedia are for information only and may not be covered by your insurance product should you make a claim.

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