What are bruises (contusions)?

A bruise is an injury that results when muscle fiber and connective tissue are crushed; blood vessels may also be torn, taking on a bluish appearance. Most bruises are minor, but some can cause more extensive damage and complications.

Bruises (contusions) occur when small blood vessels under the skin tear or rupture, most often from a twist, bump or fall. Blood leaks into tissues under the skin and causes a black-and-blue color that often turns colors, including purplish black, reddish blue or yellowish green, as the bruise heals. Most bruises are not serious and will go away on their own within two to four weeks. Sometimes, gravity causes them to spread down the body. A leg bruise usually will take longer to heal than a bruise on the face or arms. Severe bruising, swelling and pain that begins within 30 minutes of an injury may mean a more serious injury, such as a severe sprain, dislocation or fracture.

Sudden unexplained bruising or a sudden increase in the frequency of bruising may be a sign of an abnormal type of bruising that may be caused by side effects of medicine, a bleeding or clotting disorder or a medical condition.

A bruise, medically referred to as a contusion, is caused when tiny blood vessels are damaged or broken as the result of a blow to the skin. The raised area of a bump or bruise results from blood leaking from injured blood vessels into the tissues, such as muscle, as well as from the body's response to the injury. A purplish, flat bruise that occurs when blood leaks out into the top layers of skin is called an ecchymosis. Petechiae, another type of bruise, refers to very small, one to three millimeter accumulations of blood beneath the skin.

Bruises change colors over time in a predictable pattern, so that it is possible to estimate when an injury occurred by the color of the bruise. Initially, a bruise will be reddish, the color of the blood under the skin. Individuals with darker skin tones may have trouble distinguishing a bruise. After one to two days, the red blood cells begin to break down, and the bruise will darken to a blue or purplish color. This fades to green at about day six. Around the eighth or ninth day, the skin over the bruised area will have a brown or yellowish appearance, and the skin will gradually change back to its normal color.

Bruising can occur due to trauma or injury, certain medications that thin the blood (including warfarin or Coumadin® and aspirin), physical abuse, bleeding disorders (such as hemophilia), and other medical conditions, including immune disorders (such as human immunodeficiency virus (HIV)), leukemia (cancer of the blood), drug and alcohol addiction, and aplastic anemia (lack of red blood cell production).

The injury required to produce a bruise varies with age. While it may take quite a bit of force to cause a bruise in a young child, even minor bumps and scrapes may cause extensive bruising or ecchymosis in an elderly person. Blood vessels become more fragile as individuals age and bruising may even occur without prior injury in the elderly.

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A bruise occurs when broken blood vessels bleed into the tissue beneath the skin, causing local discoloration. The bruise usually occurs as a result of a fall, blow, or knock against a hard surface. Sometimes a person knows exactly how he or she got a bruise, and sometimes the bruise is a complete surprise. A bruise generally starts as a red mark and then turns from blue to brown to yellow-green as the blood is reabsorbed into the body. Some bruises are accompanied by a bump or swelling. This is most common if the bruise is on the forehead or somewhere else where the bone is very close to the skin. Most bruises are not serious, and they disappear on their own.

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A bruise is blood that has extravasated (or migrated) outside the blood vessel because of trauma. Tiny blood vessels near the surface of the skin can burst from a bump, a scrape, or injection - any kind of physical distress. Bruises change color like a mood ring as they mature (from black and blue to green to yellow) and last about one week on the face and two weeks on the body.