What are blisters?
A blister is a collection of clear fluid trapped between or beneath the top layer of skin, the epidermis. Blisters, which are often called “water blisters,” often break open and the fluid inside is released onto the skin. Blisters, also known as vesicles, can occur in all age groups and populations.
A blood blister is a specific type of blister that is due to damage to blood vessels and tissues just under the skin, which causes blood and other fluids to pool and form a bump. Blood blisters typically form after a strong pinch of the tissues, but there are other causes as well.
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In contrast to a blister, an abscess is a collection of pus, a thick, cloudy, white or yellow-colored fluid that contains white blood cells and dead tissue. An abscess is caused by the body’s response to an infection (usually a bacterial infection). A blister that becomes seriously infected can develop into an abscess.
Blisters can be caused by a wide variety of mild to serious diseases, disorders and conditions including infection, inflammation, autoimmune disorder, trauma, allergy, adverse drug reaction, and other abnormal processes. Blisters can form anywhere on the body, including inside the mouth, nose and genitals. Blisters can occur in isolation or you may develop hundreds of tiny blisters that affect several areas of the body. Blisters can be very tiny and hardly noticeable or quite large, reaching a quarter inch in diameter or larger.
Depending on the cause, a blister can go away suddenly, such as a friction blister that develops from wearing a new pair of shoes. Blisters that occur unexpectedly, worsen over time, or occur in large numbers may be a sign of a more serious condition, such as an autoimmune or infectious disease. Diseases that cause blistering of the skin are called bullous skin diseases.
Because a blister can be a sign of a serious disease or condition, you should seek prompt medical care and talk with your medical professional about a blister or blisters that are persistent or occur with swollen lymph nodes, fever, pain, joint achiness, or the development of pain, redness or pus. If you have diabetes, you should seek prompt medical care to evaluate any blisters on the feet or legs, even if they are small.
Seek immediate medical care (call 911) If you have blisters with a high fever (higher than 101 degrees Fahrenheit), difficulty breathing, a severe or electrical burn, or you have been exposed to cold temperatures or toxic chemicals, such as lye or acids.
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- Vesicles. Medline Plus, a service of the National Library of Medicine National Institutes of Health. www.nlm.nih.gov/medlineplus/ency/article/003939.htm
- Bullous pemphigoid. Medline Plus, a service of the National Library of Medicine National Institutes of Health. http://www.nlm.nih.gov/medlineplus/ency/article/000883.htm
- Porphyria. a service of the National Library of Medicine National Institutes of Health. www.nlm.nih.gov/medlineplus/ency/article/001208.htm
- Weedon D. Weedon's Skin Pathology, 3rd ed, Philadelphia: Elsevier Limited, 2010.