Follicular filament is generally defined as a primary non-inflammatory acne efflorescence.
Follicular filaments may be expressed as white pins when pressure is exerted on the nostrils, especially in persons with a seborrhoeic constitution. They consist of about 20-40 corneocytes layered on top of each other. In the center of a follicular filament a vellus hair is detectable. Bacteria, possibly Pityrosporum spores and sebum are also present.
A comedo may arise from a follicular filament.