Elizabeth Martin and Robert Hine. Latest Edition (7 ed.) Fully revised and updated, the sixth edition of this dictionary provides comprehensive coverage of biology, biophysics, and biochemistry, as well as key terms from medicine and palaeontology.
For example, if someone scratches a mole until it bleeds, the resulting lesion, a crust, is now a secondary skin lesion. The most common secondary skin lesions include: 1  crust: a crust, or a scab, is created when dried blood forms over a scratched and irritated skin lesion. 2  ulcer: typically caused by a bacterial infection or physical trauma. 3  scale: patches of skin cells that build up and then fall off the skin.
Scab is a technical anti-shibboleth. The preferred medical term is crust or eschar, the latter being Greek for scab. The edge of an eschar can keep a wound from closing by secondary intention. And an eschar is a sign that a wound is too dry to heal as fast as possible. Having noted that, a crust is the best nature can do in many situations.