Sebaceous filament
{{Infobox medical condition (new)
| name = Sebaceous filament
| synonyms = Blackhead (mistakenly)
| image = 240px
| caption = A 14 year old with characteristic black kind of sebaceous filaments on the nose
| field = Dermatology
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A sebaceous filament is a tiny collection of sebum and dead skin cells around a hair follicle, which usually takes the form of a small, yellow to off-white hair-like strand when expressed from the skin.{{Cite journal | pmid = 161830| year = 1979| author1 = Whiting| first1 = D. A.| title = Acne| journal = The Western Journal of Medicine| volume = 131| issue = 6| pages = 551–7| pmc = 1271924}}{{cite book |last1=Plewig |first1=Gerd |last2=Melnik |first2=Bodo |last3=WenChieh |first3=Chen |title=Plewig and Kligman's Acne and Rosacea |date=2019 |publisher=Springer Nature Switzerland AG |location=Basel, Switzerland |edition=4th}}{{rp|2}}
These filaments are naturally occurring, and are especially prominent on the nose.{{Cite journal | pmid = 130839| year = 1976| author1 = Plewig| first1 = G.| title = Sebaceous filaments (author's transl)| journal = Archiv für Dermatologische Forschung| volume = 255| issue = 1| pages = 9–21| last2 = Wolff| first2 = H. H.}}{{rp|64}} They are typical among those with naturally oily skin and large pores, even if those individuals have ceased to produce acne.{{rp|64}} They are not a sign of infection or any other ailment including acne,{{rp|16}} and are commonly mistaken for, though cannot form,{{rp|26}} blackheads. Expression, or squeezing, is discouraged as sebaceous filaments are a natural part of healthy human skin. As such, squeezing can lead to unintentional unnecessary harm, such as scarring or inflammation. They help to channel the flow of sebum within a given pore, allowing it to seep gradually to the surface. In 1979, David A. Whiting described them in a review in the Western Journal of Medicine as "a loose, porous mass of horned detritus".