Terminal hair

Terminal hair is the thick, long, pigmented hair anchored deep in the dermis. Scalp hair, beard, body hair after puberty, eyebrows, and eyelashes are all terminal.

Vellus hair is the opposite: short, fine, soft, lightly pigmented hair that covers most of the body. The transition between them is androgen-driven during puberty (vellus to terminal in beard, axilla, pubic area) and reversed in pattern hair loss (terminal to vellus on the susceptible scalp).

In trichoscopy, the diagnostic clue for androgenetic alopecia is variability in shaft diameter within a small scalp area: terminal hairs alongside intermediate and vellus-like hairs reflect ongoing miniaturisation.

Successful treatment with minoxidil, finasteride, or dutasteride often shows in trichoscopy as miniaturised hairs progressing back toward terminal calibre.