Comedo

"Blackhead" redirects here. For other uses, see Blackhead (disambiguation).

Comedo (Latin for glutton, plural comedones) is the primary sign of acne and consists of a widened hair follicle filled with keratin skin debris, bacteria, and sebum (oil). A comedo may be open (commonly called blackhead) or closed (commonly called whitehead).

Blackheads

Blackhead
Classification and external resources
A high resolution macro shot of a blackhead found on a male's face.
ICD-9	706.1

A male with blackheads on his nose

Blackheads are one of the common findings in acne vulgaris. Contrary to the common belief that it is caused by poor hygiene, blackheads are caused by excess oils that have accumulated in the sebaceous gland's duct. The substance found in these bumps mostly consists of keratin and modified sebum (an oily secretion of the sebaceous gland), which darkens as it oxidizes. Clogged hair follicles, where blackheads often occur, reflect light irregularly to produce a blackhead's "black" hue. For this reason, the blockage might not necessarily look black when extracted from the pore, but may have a more yellow-brown colour as a result of its melanin content.

Whiteheads

A whitehead (more commonly known as a pimple) is a non inflamed pore blocked with sebum, a symptom of acne vulgaris. In contrast to a blackhead, a whitehead is a follicle that is filled with the same material, sebum, but lacks a small opening to the skin surface. Since the air cannot reach the follicle, the material is not oxidized, and remains white.