Comedo

A comedo (plural comedones) is a clogged hair follicle (pore) in the skin.^[2]Keratin (skin debris) combines with oil to block the follicle.^[3] A comedo can be open (blackhead) or closed by skin (whitehead) and occur with or without acne.^[3] The word comedo comes from Latincomedere '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.^[1]

The chronic inflammatory condition that usually includes comedones, inflamed papules, and pustules (pimples) is called acne.^[3][4] Infection causes inflammation and the development of pus.^[2] Whether a skin condition classifies as acne depends on the number of comedones and infection.^[4] 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 noninvasive form of breast cancer, but comedo-type DCIS may be more aggressive, so may be more likely to become invasive.^[5]

Oil production in the sebaceous glands increases during puberty, causing comedones and acne to be common in adolescents.^[3][4] Acne is also found premenstrually and in women with polyendocrine metabolic ovarian syndrome.^[3] Smoking may worsen acne.^[3]

Oxidation rather than poor hygiene or dirt causes blackheads to be black.^[2] Washing or scrubbing the skin too much could make it worse, by irritating the skin.^[2] Touching and picking at comedones might cause irritation and spread infection.^[2] What effect shaving has on the development of comedones or acne is unclear.^[2]

Some skin products might increase comedones by blocking pores,^[2] and greasy hair products (such as pomades) can worsen acne.^[3] Skin products that claim to not clog pores may be labeled noncomedogenic or nonacnegenic.^[6] Make-up and skin products that are oil-free and water-based may be less likely to cause acne.^[6] Whether dietary factors or sun exposure make comedones better, worse, or neither is unknown.^[3]

A hair that does not emerge normally, an ingrown hair, can also block the pore and cause a bulge or lead to infection (causing inflammation and pus).^[4]

Genes may play a role in the chances of developing acne.^[3] Comedones may be more common in some ethnic groups.^[3][7] People of Latino and recent African descent may experience more inflammation in comedones, more comedonal acne, and earlier onset of inflammation.^[3][7]

Comedones are associated with the pilosebaceous unit, which includes a hair follicle and sebaceous gland. These units are mostly on the face, neck, upper chest, shoulders, and back.^[3] Excess keratin combined with sebum can plug the opening of the follicle.^[3][8] This small plug is called a microcomedo.^[8]Androgens increase sebum (oil) production.^[3] If sebum continues to build up behind the plug, it can enlarge and form a visible comedo.^[8]

A comedo may be open to the air ("blackhead") or closed by skin ("whitehead").^[2] Being open to the air causes oxidation of the melanin pigment, which turns it black.^[9][2]Cutibacterium acnes is the suspected infectious agent in acne.^[3] It can proliferate in sebum and cause inflamed pustules (pimples) characteristic of acne.^[3]Nodules are inflamed, painful, deep bumps under the skin.^[3]

Comedones that are 1 mm or larger are called macrocomedones.^[10] They are closed comedones and are more frequent on the face than neck.^[11]

Solar comedones (sometimes called senile comedones) are related to many years of exposure to the sun, usually on the cheeks, not to acne-related pathophysiology.^[12]

Using non-oily cleansers and mild soap may not cause as much irritation to the skin as regular soap.^[13][14] Blackheads can be removed across an area with commercially available pore-cleansing strips (which can still damage the skin by leaving the pores wide open and ripping excess skin) or the more aggressive cyanoacrylate method used by dermatologists.^[15]

Squeezing blackheads and whiteheads can remove them, but can also damage the skin.^[2] Doing so increases the risk of causing or transmitting infection and scarring, as well as potentially pushing any infection deeper into the skin.^[2] Comedo extractors are used with careful hygiene in beauty salons and by dermatologists, usually after steaming the face or washing in warm water.^[2]

Complementary medicine options for acne in general have not been shown to be effective in trials.^[3] These include aloe vera, pyridoxine (vitamin B₆), fruit-derived acids, kampo (Japanese herbal medicine), ayurvedic herbal treatments, and acupuncture.^[3]

Algunos tratamientos para el acné se dirigen específicamente a la infección, pero otros también están dirigidos a la formación de comedones. ^{[ 16 ]} Otros eliminan las capas muertas de la piel y pueden ayudar a desobstruir los poros. ^{[ 2 ] [ 3 ] [ 4 ]}

Los dermatólogos suelen poder extraer comedones abiertos con un traumatismo mínimo en la piel, pero los comedones cerrados son más difíciles. ^{[ 3 ]} El tratamiento con láser para el acné podría reducir los comedones, ^{[ 17 ]} pero también se sabe que la dermoabrasión y la terapia con láser pueden causar cicatrices. ^{[ 10 ]}

Los macrocomedones (de 1  mm o más) pueden ser extirpados por un dermatólogo mediante instrumental quirúrgico o cauterizados con un dispositivo que utiliza luz. ^{[ 10 ] [ 11 ]} El fármaco para el acné isotretinoína puede provocar brotes severos de macrocomedones, por lo que los dermatólogos recomiendan su extirpación antes de comenzar el tratamiento y durante el mismo. ^{[ 10 ] [ 11 ]}

Algunas investigaciones sugieren que los medicamentos comunes para el acné, como los retinoides y el ácido azelaico, son beneficiosos y no provocan un aumento de la pigmentación de la piel. ^{[ 18 ]} Los retinoides solo deben aplicarse por la noche, ya que a) la luz los degrada y b) el ciclo de reparación de la piel alcanza su punto máximo durante la noche. También se debe usar protector solar durante el día, ya que la piel se vuelve más sensible a los rayos UV. ^{[ 19 ]}

El síndrome de Favre-Racouchot se produce en la piel dañada por el sol e incluye comedones abiertos y cerrados. ^{[ 20 ]}

El nevus comedónico , o nevus comedónico, es un hamartoma benigno(mancha de nacimiento) de la unidad pilosebácea alrededor de la glándula sebácea en la piel. ^{[ 21 ]} Presenta folículos pilosos abiertos y dilatados con tapones de queratina oscura que se asemejan a comedones, pero que en realidad no lo son. ^{[ 21 ] [ 22 ]}

La enfermedad de Dowling-Degos es un trastorno genético de la pigmentación que incluye lesiones similares a comedones y cicatrices. ^{[ 23 ] [ 24 ]}

Los comedones disqueratósicos familiares son una afección genética autosómica dominante poco frecuente , caracterizada por pápulas queratósicas (duras) y lesiones similares a comedones. ^{[ 25 ] [ 26 ]}

• Rines, George Edwin, ed. (1920). «Comedones»  . Enciclopedia Americana .
• Causas de los puntos negros, tratamiento y prevención. Archivado el 27/01/2020 en Wayback Machine.