Bruising occurs when small blood vessels under the skin break, usually due to an impact or injury. This causes blood to leak into the surrounding tissue, resulting in a discoloration that can range from red to purple, blue, or yellow as it heals. Bruises can vary in size and may be tender to the touch. Most bruises heal on their own within a few days to weeks. Common causes include falls, bumps, or sports injuries. While most bruises are harmless, frequent or unexplained bruising may indicate an underlying health issue, and consulting a healthcare professional is advisable in such cases.