What Causes Blood Blisters?

A standard blister that appears on the skin is usually filled with a white-yellow liquid (pus). However, blisters can be filled with many different types of fluids that include serum, plasma, and even blood. A blood blister is any kind of raised skin with blood underneath it. Even though these blisters have an odd appearance to them that makes it seem like they are harmful, blood blisters don't usually cause health complications and should disappear completely within several weeks, which is true even if they don't obtain treatment for the blister. These blisters vary in size and are filled with a mixture of blood from a ruptured blood vessel and clear liquid. When individuals are affected by one of these blisters, the color of the blister can be reddish, purplish, or even black. In most cases, they will start out with a bright red before becoming darker over time. These blisters can appear in areas of the body where high amounts of pressure are placed, including the feet, hands, mouth, and certain bony areas.