2016, Cheryl Carver, Knowing the Difference Between Scabs and Eschar:
...stable intact eschar on the heels should not be removed. Blood flow in the tissue under the eschar is poor and the wound is susceptible to infection. The eschar acts as a natural barrier to infection by keeping the bacteria from entering the wound. If the eschar becomes unstable (wet, draining, loose, boggy, edematous, red) it should be debrided according to the clinic or facilityprotocol
(loose or obsolete) Any hard, dark, commonly flattened or sunken lesion or crust, especially on a burn, abscess, infection, wound; commonly a coagulation of blood or exudations, not necessarily involving dead or necrotic tissue.
1779, John Andree, Observations on the Theory and Cure of the Venereal Disease: