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. These filaments are naturally occurring, and are especially prominent on the nose. They are commonly mistaken for blackheads. In 1979, David A. Whiting described them in a review in the Western Journal of Medicine as "a loose, porous mass of horned detritus".