Toronto Blue Jays right fielder José Bautista can tell you: Bruising is no fun.
But how and why we bruise is actually a pretty interesting process, as Amy Shira-Teitel explains in today's DNews dispatch.
What we see as a bruise is essentially blood trapped just under the skin, a kind of internal bleeding that's usually not a serious medical problem. The blood comes from broken capillaries, the tiny blood vessels near the surface of the skin.
Physical trauma typically causes those capillaries to burst, and the internal bleeding works pretty much the same as external bleeding. Platelets rush to the site of the bruise and start clotting up blood, keeping things from getting out of hand.
That's the dark-purple phase of the bruise. The sickly yellow color that gradually emerges comes from microphages, vampiric little immune cells that digest blood and eventually clear up the bruise.
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Some people bruise more easily than others, and multiple factors come into play here. Age, sun exposure and genetic tendencies can result in thinner skin, quite literally, making capillaries weaker and trauma-induced bruising more likely.
People with high body fat can be more prone to bruising, but so can athletes. Heavy exercise causes tiny muscle tears that can rupture capillaries. Blood thinners like aspirin, or anticoagulant medication, can cause bruises to last longer by impeding the clotting mechanism.
Then there's the serious stuff. Lupus, cirrhosis and chronic infections can impede clotting, as can certain kinds of malnutrition. Hereditary bleeding disorders -- like hemophilia and Von Willebrand disease -- prevent blood coagulation and can even cause spontaneous bruising.
As can second basemen from Texas.
-- Glenn McDonald
Greatist: Why You Bruise So Easily
Hematology.org: Bleeding Disorders
University of Michigan: Bruises and Blood Spots Under the Skin