A purulent exudate is an inflammatory exudate with a high concentration of leukocytes - predominantly neutrophils - dead cell matter and inflammatory molecules e.g. cytokines, lysozymes. The degree of enzyme proteolysis determines the thickness of the fluid.
Clinically, pus is usually confined to the area of inflammation as demarcated by a pustule or abscess enclosed within the fibrous pyogenic membrane.
It can can assume a yellow, green or white colour. The last is associated with Staphylococcal sp. infection.