Eschar is a type of necrotic tissue that can develop on severe wounds. It is typically dry, black, firm, and usually adhered to the wound bed and edges. Eschar can occur on  full thickness injuries, which are wounds that extend below the epidermis and dermis. Examples include third degree burns, or stage three and four pressure injuries. Additionally, eschar can be present on some skin rashes associated with infections, such as ecthyma gangrenosum, scrub typhus, rickettsialpox, and anthrax.  Eschar differs from a scab, which is formed when platelets and fibrinogen form a fibrin mesh, trap red blood cells on surface wounds, and form a clot that dries into a scab. Instead, eschar is formed when slough, or other dead tissue debris, from a full thickness wound dries out and hardens.