Hello, Blood blisters are collection of blood underneath the skin due to rupture of small blood vessels. they occur due to friction, tight clothing, heavy rubbing, pinching, some times due to infection. usually blood blisters go on their own, no remedy is needed. But if the blister is large or bursts there is a chance of it getting infected, then you have to have antibiotics. Clod compression on blood blister is a good mode of relieving pain and reduce size of blood blister at acute stage. Hope this helps. Thank you .