What is Pus? Understanding Inflammation and Infection

The yellowish substance that builds up around an injury in the process of inflammation is pus. Pus is a thick, creamy fluid that is made up of dead white blood cells, bacteria, and other debris. It is produced when the body's immune system fights off an infection. Pus can be a sign of a bacterial infection, and it is important to see a doctor if you have pus draining from a wound.