Which skin condition involves the presence of pus?

The presence of pus is a hallmark characteristic of a pustule, which is a small, inflamed, elevated lesion filled with a purulent material. Pustules commonly occur in various skin conditions, including acne, where they form as a result of blocked hair follicles becoming infected with bacteria. The accumulation of pus—comprised of dead white blood cells, bacteria, and tissue debris—indicates a localized inflammatory response, demonstrating the body's attempt to fight off infection.

In contrast, the other skin conditions listed do not involve pus. A papule is a solid, elevated lesion that does not contain pus, while a verruca, commonly known as a wart, is caused by a viral infection and appears as a benign growth without pus. Sepsis, although a serious medical condition involving a systemic inflammatory response to infection, is not directly characterized by pustule formation on the skin. Thus, the identification of pustules as the correct option highlights their specific association with pus and localized infection.