What is "comedo"

Comedo \Com"e*do\, n.; pl. Comedones. [L., a glutton. See Comestible.] (Med.) A small nodule or cystic tumor, common on the nose, etc., which on pressure allows the escape of a yellow wormlike mass of retained oily secretion, with a black head (dirt).

"blackhead," etc., 1866, from Latin comedo "glutton," from comedere "to eat up" (see comestible). A name formerly given to worms that devour the body; transferred in medical use to secretions that resemble them.

n. a blackhead

1. n. a black-tipped plug clogging a pore of the skin [syn: blackhead]

2. [also: comedones (pl)]

A comedo is a clogged hair follicle (pore) in the skin. Keratin (skin debris) combines with oil to block the follicle. A comedo can be open (blackhead) or closed by skin (whitehead), and occur with or without acne. The word comedo comes from the Latin comedere, meaning "to eat up," and was historically used to describe parasitic worms; in modern medical terminology, it is used to suggest the worm-like appearance of the expressed material.

The chronic inflammatory condition that usually includes both comedones and inflamed papules and pustules ( pimples) is called acne. Infection causes inflammation and the development of pus. Whether or not a skin condition classifies as acne depends on the amount of comedones and infection. Comedones should not be confused with sebaceous filaments.

Comedo-type ductal carcinoma in situ (DCIS) is not related to the skin conditions discussed here. DCIS is a non-invasive form of breast cancer, but comedo-type DCIS may be more aggressive and so may be more likely to become invasive.