A somewhat misleading term, as all blister
s are really "blood blisters." Ordinary blisters only contain clear, colorless serum
, however, which is not ordinarily recognized as blood
Blood blisters, on the other hand, contain whole blood, complete with the hemoglobin that gives its characteristic red color. They are typically formed by sudden, bruising impacts or pinching forces, rather than the gradual effects of friction that cause ordinary blisters. The blood is present due to ruptured capillaries just beneath the skin. In some cases, a blood blister will form on a foot where heavy callouses develop over a previously blistered area, increasing friction to the point where capillaries can burst.
Treatment is the same as for a common blister - protect the blistered area from further stress, and don't pop it, as this increases the risk of infection. When it dries up, the dead skin will peel off in a few weeks.