Skin bruises, which are the most common type of bruise, develop when small blood vessels that are directly under the skin are broken or ruptured. This usually happens from blunt trauma, such as being punched in the arm or smacking your shin against a table. Bruises develop slowly and can last for up to 1 month. Once the blood vessels have ruptured, the blood slowly seeps into the surrounding area. At first, the bruise appears as a reddish area. After a day or two, the bruise will turn the skin black and blue, as the damage to the tissue surrounding the broken blood vessels becomes more apparent. Over time, the body reabsorbs the blood, which makes the bruise turn a yellowish-green color. A bruise may be very small and may blend in with the texture of the skin, or it may be large, swollen and painful. Within days to a week or so, the bruise becomes more purple. As it heals, it becomes brownish-yellow. Generally, bruises heal and disappear within 2 to 3 weeks.
Bone and Muscle Bruises
Bones and muscles can also be bruised. Both are more serious than skin bruises and are usually caused by more serious accidents such as sports injuries, car accidents and recreational injuries, such as a skiing accident.
Bone bruises usually occur in the medullary portion of the bone, or the area between the joints. A bone bruise can have swelling and bleeding at the side of the damaged blood vessels, and is usually quite painful. Like the more common skin bruise, they can take a month or more to heal. Muscle bruises occur when the muscles take a direct blow and their blood vessels are damaged without breaking the skin. Pain and swelling are common symptoms, along with stiffness and limited motion. Again, they can take up to a month or more to heal.
Frequent or Serious Skin Bruising
Some people tend to bruise easily, which can mean that they have thin skin, anemia or other health issues. In fact, these bruises can develop without an associated trauma injury, and can be a sign of more serious health issues. In such cases, a doctor should be consulted. In addition, many people may have bruising that lingers more than 14 days. Again, a doctor should be consulted in these cases.
Bruises that appear behind an ear after a head injury can signify a skull fracture, in which case a doctor should be contacted immediately. The same can be said for if a bruise develops as a result of a back injury, especially the lower back, combined with blood in the urine. This can signify damage to the kidneys. Once again, in this case, a doctor should be seen immediately.