A bruise is a mark on your skin caused by blood trapped under the surface. It happens when an injury crushes small blood vessels but does not break the skin. Those vessels break open and leak blood under the skin. Most bruises are not a cause for concern and will go away on their own. Home treatment may speed healing and relieve the swelling and soreness that often accompany bruises that are caused by injury. However, severe bruising, swelling, and pain that begin within 30 minutes of an injury may mean a more serious problem, such as a severe sprain or fracture. Bruises Causes Bruises can occur in some people who exercise rigor bass guitar lessons ously, such as athletes and weight lifters. These bruises result from microscopic tears in blood vessels under the skin. Certain illnesses and diseases can cause bruising. Unexplained bruises in children may be the result of child abuse. If you suspect a child is being abused, ask a doctor or community health center how to report your concerns. Symptoms of Bruises The main symptoms are pain, swelling, and skin discoloration. The bruise begins as a pinkish red color that can be very tender to touch. It is often difficult to use the muscle that has been bruised. For example, a deep thigh bruise is painful when you walk or run.