Trichostasis spinulosa is a common but rarely diagnosed disorder of the hair follicles that clinically gives the impression of blackheads, but the follicles are filled with funnel-shaped, horny plugs which are bundles of vellus hairs.
Diagnosis
Standard skin surface biopsy (SSSB) is a non-invasive method used for diagnosis.
References
Trichostasis spinulosa Wikipedia(Text) CC BY-SA