A blood blister is a specific blister that is formed when blood vessels beneath the skin are ruptured, but the surface of the skin isn’t actually broken. As a result, the body basically bleeds underneath the skin, and blood pools up beneath the skin, along with lymph and other fluids. A blood blister will usually have a very dark red color, sometimes approaching black. If the wound heals, but the blood remains trapped, it may dry out and eventually become a slightly harder consistency.
Depending on the wound, a blood blister can also be a source of quite a bit of pain. This is because often some level of bruising takes place during the trauma that broke the blood vessels, and the blister keeps pressure pushing down on the bruise at all times. In these cases, even slightly touching it can cause a severe pain, and many people break open their blisters to relieve the pressure and the pain.
The most common cause of a blood blister is a trauma in which the skin is pinched in something, often something like a pair of scissors or pliers, or the hinge of a door or some other object. The blood vessels are therefore ruptured, but in the absence of a pulling or cutting wound, the skin itself is not breached. This allows the blood to pool up and form a blister. In some cases, a blood blister may be formed by some sort of steady wear, such as a pair of shoes that don’t fit properly being worn on a long hike. They may also be formed as a result of frostbite, in which the blood vessels beneath the skin burst from the expansion of the liquid in them, but the skin is never broken.
Ideally, a blood blister should be treated by protecting it from bursting, and protecting it from further wear. Initially, a cold pack can be used to help dull the pain, and to stop the body from reacting as strongly with an immune response. Later, Epsom salts may be used to make the swelling go down. If possible, the entire area should be elevated, to help blood drain from the blister, and it should be bandaged and changed and cleaned regularly.
A blood blister really shouldn’t be popped, but in some cases this may be unavoidable. Blisters gained from excessive walking, for example, may burst if one has to keep walking on them. In this case, it’s important to clean the wound thoroughly, and disinfect it, then bandage it cleanly and well, and to continue cleaning and reapplying bandages as it heals. A blood blister can be an easy source of infection, especially given that most occur either on the hands or feet.
For those who are engaging in an activity likely to give them a blister, such as soldiers on a long march, putting extra padding or blister pads on areas prone to blisters is an excellent idea. If blisters do form, and must be taken care of while continuing to traumatize the wound, one technique often used by soldiers is to thread a piece of string through the blister, so that it can drain slowly, and the layers of skin can form a seal and stick together. Although not recommended, in some cases this may be the only option available, and if it is undertaken great pains must be taken to make sure infection doesn’t develop.