A bruise, also known as a contusion, occurs when an injury crushes blood vessels but does not break the skin. The broken vessels leak under the skin. Pooled blood forms a blemish that changes color and gradually fades away as the body reabsorbs the collected blood.2 ...
When you have a swelled bruise accompanied with severe pain, particularly if you were under a blood-thinning medication. When you have frequent unexplained bruising. When you have a painful bruise under your fingernail or toenail. When a bruise fails to improve and fails to clear within 2-4 ...