A blood blister is a type of blister that develops when blood vessels are damaged near the surface of the skin. Blood blisters form after a pinching or bruising injury that does not actually break the skin. Since the blood cannot escape through an open wound, it collects beneath a bubble under the surface of the skin.

Blood blisters are very similar to friction blisters. They usually do not require medical treatment. The blister will heal on its own within three to seven days.

Causes and symptoms of blood blisters

Blood blisters are caused by a rupture of the blood vessels near the surface of the skin. This rupture develops from injuries that pinch the skin, like getting your toe caught in a door. Blood blisters are also caused by severe force from kicking something hard or stubbing your toe. They may develop also from persistent pressure from inappropriate footwear.

A blood blister can be very painful when it first develops. Blood blisters resemble friction blisters in size and shape; the only difference is they appear darker from the small amount of blood trapped between layers of skin.

Blood blister treatment

Blood blisters usually do not require medical attention. They are very similar to normal skin blisters in the way that they heal. It is best to avoid popping blood blisters; if left alone, new skin will form beneath the blister and they will heal on their own within a week’s time. If a blood blister is accidentally punctured, only a small amount of blood will escape, but skin will feel raw and extremely painful.

Blood blisters should be covered with a sterile, soft dressing and washed frequently to keep them clear of irritants. If a blood blister breaks, it should be treated with antiseptic ointment to prevent infection. It is important to leave the skin over a blood blister intact, even if it ruptures. That layer of skin provides natural protection from bacteria.

Blood blisters that fail to heal on their own may require treatment. If there are any signs of infection near the blister like warmth, redness, or inflammation, contact a physician immediately.