A bruise is also called a contusion (say: ken-too-zhen), and it forms after a hard enough bump to the soft tissues under your skin. When these tissues are injured, small veins and capillaries (the tiniest blood vessels) under the skin sometimes break. These blood vessels then leak out red blood cells.

The red blood cells that collect under your skin are what cause that bluish, purplish, reddish, or blackish mark. That’s where black-and-blue marks get their name – from their color on the skin.

Some people bruise easily whereas others may have tougher skin tissue. Despite the many ways you can get them, bruises pretty much go through the same colorful changes as the body begins to heal itself.

A bruise will turn nearly all the colors in the rainbow before it finally fades away. The color changes mean that your body is metabolizing (say: meh-tab-ah-lie-zing), or breaking down, the blood cells in the skin. This is the chemical process that your body goes through to repair itself.

Imagine you’re hit with a baseball in the leg. Ouch! Your body will go through the following phases:

• First, you’ll probably have a bump that will probably look red or purplish and tender. The bump might swell from the blood collecting under the tissue.
• After a couple of days, the bruise will look blue (or even blackish).
• After 5 to 10 days, it may look greenish or even yellow.
• After 10 to 14 days, the bruise will most likely be a light brown, then get lighter and lighter as it fades away.

Most bruises will disappear after 2 weeks, and some go away even sooner.