Blood blisters can look alarming when they suddenly appear. Unlike ordinary blisters filled with clear fluid, these raised spots contain trapped blood beneath the skin, giving them a dark red, purple, or even black appearance. While they often seem serious at first glance, most blood blisters are minor injuries that heal naturally with proper care.

A blood blister forms when small blood vessels, known as capillaries, break beneath the skin’s surface while the outer layer remains intact. The blood becomes trapped underneath, creating a swollen pocket that is usually tender to the touch. These blisters commonly appear on areas exposed to pressure or friction such as fingers, palms, toes, and soles of the feet, and sometimes inside the mouth.

In most cases, blood blisters are caused by everyday trauma like slamming a finger in a door, wearing tight shoes, or repeated rubbing from tools or sports equipment. Inside the mouth, they may appear after biting the cheek or tongue, dental procedures, or irritation from dental appliances. Some people are also more prone to them due to fragile skin, circulation issues, diabetes, or blood-clotting disorders.

A blood blister is usually easy to recognize as a raised, dark-colored bump that may feel tender, sore, or slightly swollen. The discomfort is typically temporary, and most blisters heal within one to two weeks. While it may be tempting to pop it, experts advise against doing so because the skin acts as a natural barrier against infection and helps the healing process.

If a blood blister bursts on its own, it should be cleaned gently with soap and water, treated with antiseptic, and covered with a clean bandage. Reducing pressure on the area, using a cold compress, and avoiding irritating activities can help speed recovery. Medical attention is recommended if the blister becomes infected, very painful, unusually large, or fails to heal within two weeks.