Why does pus form during acute inflammation?

During acute inflammation, pus forms as a result of the body's immune response to infection or tissue injury. When pathogens—such as pyogenic bacteria—invade connective tissue, they release toxins that damage local cells and trigger an inflammatory response.12

In response, white blood cells, specifically neutrophils, migrate from the bloodstream into the affected tissue in large numbers to ingest and destroy the invaders through phagocytosis. Because these neutrophils have a short life span, they die in great numbers after completing their mission.34

Pus is the resulting viscous, opaque fluid composed of these dead and dying neutrophils, cellular debris, bacteria, and extracellular fluid that has leaked from blood vessels. This process, known as suppuration, typically occurs when the agent causing the inflammation is difficult for the body to eliminate.512