HAIR DISEASES

A few common causes of hair loss account for the vast majority of case s. A well-directed history and simple physical examination is often su fficient to make a diagnosis. Laboratory testing is often unnecessary. A scalp biopsy can be useful, but only if processed and interpreted c orrectly. Androgenetic alopecia, alopecia areata, senescent alopecia, telogen effluvium, traction alopecia, trichotillomania, and cosmetic h air damage are common causes of nonscarring alopecia. Discoid lupus er ythematosus, lichen planopilaris, and central, centrifugal scarring al opecia are the most common forms of scarring hair loss.