What is the most accurate description of a blackhead?

A blackhead is accurately described as an open comedone. This term refers to a type of acne lesion that forms when a hair follicle becomes clogged with excess oil and dead skin cells. The key characteristic of a blackhead is that the clogged pore remains open at the surface, allowing the material within to oxidize and create a dark appearance.

This oxidization occurs when the melanin in the sebum reacts with oxygen in the air, leading to the distinctive black color. Open comedones are typically not inflamed, which differentiates them from other forms of acne, such as papules or pustules that result from inflammation.

The other descriptions do not accurately capture the nature of a blackhead. A closed comedone, for instance, refers to a clogged pore that is not exposed to air, leading to a white appearance. Pore congestion is a broader term that may refer to various forms of clogged pores without specifying whether they are open or closed. The term blemish can describe a variety of skin imperfections, not specifically identifying it as a blackhead.