Bruises are caused by small torn blood vessels under the skin and may occur after a bump or a fall. Blood seeps into tissues, turning them reddish, then black and blue. Most bruises go away within 2 to 3 weeks, after turning yellow, green, and brown. Home treatment may speed healing.

Bruising or discoloration can be more serious when it:

• Develops within 30 minutes of the injury. This can occur with a severe bruise (contusion), dislocated jaw, broken facial bone, or broken lower jawbone (mandible).
• Occurs on the cheek or on the floor of the mouth. This can be a sign of a broken jaw.
• Occurs behind an ear ("Battle's sign") or around both eyes ("raccoon eyes"). If bruising occurs in these areas and is not caused by direct injury to both eyes or the forehead or behind an ear, it can be a symptom of a skull fracture—especially if a head injury was also present—a broken cheekbone (zygomatic fracture), or a broken nose.
• Occurs in people who have conditions or who take medicines that interfere with blood clotting, such as warfarin, heparin, or aspirin. There is an increased chance of bleeding into injured joints or bones.