Which term describes a painful, pus-filled boil associated with a single hair follicle?

The term that describes a painful, pus-filled boil associated with a single hair follicle is "furuncle." A furuncle, commonly known as a boil, results from an infection of the hair follicle, usually caused by bacteria, most often Staphylococcus aureus. The area becomes inflamed, painful, and filled with pus as the body responds to the infection.

Understanding how a furuncle develops is important for esthetics professionals, as it can affect the skin's appearance and may require specific treatments to manage inflammation and infection. In contrast, other terms in the options refer to different skin conditions. A fissure is a small slit or crack in the skin, an ulcer is a sore that involves the epidermis and dermis, and excoriation refers to an area where the skin has been scraped or abraded. Each of these terms describes distinct conditions that do not involve a boil or hair follicle infection, highlighting why "furuncle" is the accurate choice.