An abscess is a localized, encapsulated, accumulation of solid or liquid material. This material represents tissue breakdown products.
Abscesses occur when microorganisms, or foreign objects, or both, gain entrance into body tissues.
The resultant tissue reaction causes an accumulation of purulent exudates in the tissue, with components as described above. At this early point, the affected area is best described as a cellulitis. If the cellulitis is not quickly resolved, or if the accumulating debris is not promptly discharged to an external body surface, then the body will attempt to wall off the affected area by forming a capsule of fibrin around it. Fibrin is gluey, web-like type of protein that also serves as a main component of scabs. Once the fibrin capsule is complete, the cellulitis is said to have become an abscess.