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.
Once a scab is formed, the scraped area usually remains dry and does not ooze fluid. 1  A scab that forms over an area that moves, such as a joint, may crack and a few drops of clear yellowish to pinkish fluid may ooze from the wound. 2  A cracked scab may be uncomfortable, and an infection can develop under the scab.