A bruise is when you suffer an injury that damages blood capillaries, but doesn't break the skin, or at least the skin directly over them. Spilled blood under the skin has to be cleaned up, which involves a complicated timeline in which various body processes break down the blood cells into smaller components that can be washed away eventually. Bruises can be red, blue, purple, black, green, yellow, and even other shades as they heal. But the timeline and the appearance of a healing bruise can vary widely, depending on factors like the depth of the injury, the amount of fat under the skin, and the color of the skin. Most research on bruises has been done on caucasian skin, which is less white than it is transparent. Bruises can seem to move away from the injury as the remains of the bleeding are cleared away. They can vary within the same person, too. When I was temporarily taking a blood thinner, my everyday activities made me look like a beating victim. Read about the colors of bruises and what causes them to look that way at TheScientist. -via Damn Interesting
(Image credit: Famartin)