What is a "scab"?

A scab is a protective crust that forms over a wound or cut as it heals. When the skin is injured and bleeding occurs, the blood thickens and dries, forming a hard layer that shields the wound from dirt and bacteria. Scabs help prevent infection and allow the underlying tissue to repair itself. They eventually fall off on their own once the skin underneath is healed. It is important not to pick at scabs, as doing so can cause scarring or reopen the wound.