Bruises (BROO-zes) are discolorations on areas of the skin. They are caused by injuries that crush and break tiny blood vessels called capillaries * without breaking the skin. The injured vessels leak blood underneath the skin, which causes the discoloration.
At age 10, Mac was the best skateboarder in his neighborhood. He was a street boarder, always skating to and from school, to his friends' houses, to the park. When possible, he skateboarded in the street, deftly jumping onto the sidewalk when a car approached. Mac always wore a helmet, but he was glad that, unlike most of his friends' parents, his parents did not insist that he wear other protective gear—kneepads, elbow pads, and wrist guards.
One day while skateboarding down the sidewalk, Mac saw that the road had cleared of traffic. He leaped down off the curb—right into the path of a bicycle. The bicyclist swerved to avoid him, but his front wheel skimmed the edge of Mac's board. Mac and his board went flying. Mac's left knee hit the pavement hard! Mac crawled over to the curb with his board. His knee throbbed. The bicyclist came over and asked if he was okay. Mac grimaced, but did not cry, and answered that he was fine. Mac touched is knee, and it hurt even more. The skin was not broken, and there was no bleeding, although it was a bit scraped. But as Mac watched, his knee turned reddish. Mac grabbed his board and hobbled home.
At home, Mac's mom had him lie down on the sofa. She put pillows under his leg to raise his knee up above the level of his heart. Then she draped a bag of frozen peas over the bruised knee. Slowly, the pain and swelling began to subside. But the next morning, Mac's knee looked much worse: it had turned an ugly bluish-purple, although it no longer hurt unless he accidentally banged it on something. Five days later, his bruised knee had turned yellowish-brown. Finally, after a couple of weeks, the bruise faded away, and Mac's knee looked as good as new.
Bruises are injuries to soft tissues of the body. They are also called contusions (kun-TOO-zhuns), hematomas (hee-mah-TOE-mahs), or ecchymoses (eh-ky-MOE-ses). Bruises are most often caused by blows to the body; by collisions with other people or inanimate objects; or by falls, sports injuries, or automobile accidents. Although harder blows generally cause larger bruises, sometimes even a minor bump that goes unnoticed can result in a substantial bruise. Bruises are especially common on the arms and legs. Bruises often cause swelling and can be quite painful.
Bruises occur when muscle fibers and connective tissue under the skin are crushed and capillaries break. Red blood cells leak out of the broken capillaries and are trapped under the skin, turning the skin reddish. As the bruise heals, the body breaks down or metabolizes (meh-TAB-ohlye-zes) the blood cells, and the bruise turns from red to “black and blue” and then to yellowish-brown.
There are three types of bruises:
Bruises are very common, although some people bruise more easily than others, depending on the toughness of their skin. Females tend to bruise more easily than males. People also bruise more easily as they age, because the skin becomes thinner, blood vessels become more fragile, and older people lose some of the protective fatty layer under the skin that cushions the blood vessels. People taking blood-thinners such as aspirin, warfarin (Coumadin), clopidogrel (Plavix), or other anticoagulants or anti-platelet medications to reduce the risk of blood clots usually bruise more readily. This is because it takes longer for the blood to clot after capillary damage, so more blood leaks out under the skin. Some dietary supplements, such as ginkgo and fish oil, have blood-thinning effects that can increase the risk of bruising. Corticosteroids * that are taken orally or applied to the skin to treat many different conditions can cause the skin to thin, making it easier to bruise. Certain diseases and conditions also cause easy bruising.
The main signs and symptoms of bruises are pain, swelling, and discoloration of the skin. At first, a bruise is pinkish-red from the blood under the skin and very tender to the touch. If the bruise is deep in a muscle, it can be hard to use that muscle; for example, a deep thigh bruise can make if very painful to walk or run. As the pooled blood from broken capillaries breaks down and is reabsorbed by the body, a bruise can go through a rainbow of color changes. One or two days after a bruise first appears, the hemoglobin (the oxygen-carrying protein in the blood) changes color, and the bruise turns from reddish to bluish-purple or blackish. After five to ten days, the bruise turns greenish-yellow, before finally returning to normal skin color. It is possible to guess the age of a bruise by its color. Most bruises last about two weeks, but sometimes they can take months to fade away.
Bruises are usually readily diagnosed by a simple physical exam. If a more serious injury, such as a broken bone, is suspected, x-rays or computed tomography (CT or CAT) scans may be required.
Most bruises are harmless and disappear without treatment, although healing may take longer in older adults. Bruises are most often treated at home with first aid:
Although minor bruises can be readily treated with first aid, a doctor should be consulted if:
Extreme pressure or pain in a bruised body part could be a symptom of compartment syndrome. This is a rare, life-threatening emergency in which increased pressure within a muscle compartment interferes with blood flow and can starve the tissue for oxygen.
Bruises can be difficult to prevent. However, since they usually result from injuries, the risk of bruises can be reduced by following safety recommendations. These include:
Rhatigan, Joe. Ouch!: The Weird & Wild Ways Your Body Deals with Agonizing Aches, Ferocious Fevers, Lousy Lumps, Crummy Colds, Bothersome Bites, Breaks, Bruises & Burns & Makes Them Feel Better. Watertown, MA: Imagine!, 2013.
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Boyd, Kierstan. “What Is a Black Eye?” American Academy of Ophthalmology. http://www.aao.org/eye-health/diseases/black-eye (accessed March 25, 2016).
MedlinePlus. “Bruise.” U.S. National Library of Medicine, National Institutes of Health. https://www.nlm.nih.gov/medlineplus/ency/article/007213.htm (accessed March 25, 2016).
American Academy of Family Physicians. PO Box 11210, Shawnee Mission, KS 66207-1210. Telephone: 913-906-6000. Toll-free: 800-274-2237. Fax: 913-906-6075. Website: http://www.aafp.org (accessed March 25, 2016).
* capillaries are the smallest blood vessels that connect the arterioles and venules and provide oxygen to tissues.
* corticosteroids (KOR-ti-ko-STERoids) are medications such as hydrocortisone for reducing inflammation and suppressing the body's immune response.