scab

A scab, in medical terms, is a crust that forms over a skin wound as part of the healing process. It is made up of dried blood, serum, fibrin, and inflammatory cells, and serves to seal the wound, reduce fluid loss, and provide a barrier against infection while new tissue forms beneath it.

Scab formation begins after injury when blood vessels are damaged and platelets accumulate to form a plug. The coagulation cascade produces a fibrin mesh that traps blood cells and fluid; as this clot dries, it forms the crust known as the scab. The process typically begins within hours and continues as the wound stabilizes.

While the scab remains, cells at the wound margins migrate to cover the wound, and new skin often develops underneath. The scab gradually loosens and is shed or falls off once the underlying tissue has healed, sometimes leaving a scar.

Care and considerations: Do not pick at scabs, as this can reopen the wound and increase the risk of infection or scarring. Keep the area clean and moisturized as directed by medical advice; seek care if the wound becomes red, grows warm, oozes pus, or is accompanied by fever, or if a scab covers a large area or does not improve.

Other uses: In common language, scab can also refer to a crusty patch on the skin; it is also used to describe a person who continues to work during a strike.