There can be no doubt that life without bruises is noticeably better than life with them, but most bruises are not considered especially dangerous. That's not to suggest that severe bruising cannot lead to other complications such as blood clots, nerve damage and loss of mobility, however. These complications can be much more dangerous than the bruises themselves, but they are rarely life-threatening.
Most bruises are caused by some form of blunt force trauma to blood vessels under the skin. When these blood vessels break open, blood begins to pour into the surrounding tissue. This blood pools under the skin and initially looks dark purple or deep red. The pain associated with these wounds is caused by the damaged nerves in the area and the pressure of the blood as it pools. This pain can be treated with over-the-counter anti-inflammatory medications, often called non-steroidal anti-inflammatory drugs.
Blood clots may form in the area, but since the clotted blood is not in the actual circulatory system, the chances of a stroke or heart attack are very slim. The blood clots themselves have nowhere to go and no way to get there, so they tend to remain in the pools of blood we see as bruises. Eventually the body will absorb the blood and the bruises should reduce in size and pain level. Any blood clots that may have formed should also be dissolved naturally and absorbed. There are occasions when blood clots could create an excessive build-up of calcium and the deposits may have to be removed surgically or through prescription medications.
The most dangerous spot for bruises to form is possibly the head and neck region. Head injuries tend to bleed heavily because of the abundance of blood vessels. A blunt force injury to the skull could create a serious form of bruise called a hematoma. A hematoma can be very susceptible to blood clots and other complications associated with internal bleeding.
As bad as these wounds may appear to be, especially during the first few hours following a trauma, they should heal on their own in time. Sometimes the pressure of the blood-filled tissues can affect or damage nerves in the local area, and those damaged nerves in turn can hamper muscle movement. If the bruises are near major joints, mobility may be temporarily affected until the swelling and pressure are reduced. If a wound does not appear to heal within a reasonable amount of time, the injury may have to be examined or re-examined by a medical professional.