Alopecia means hair loss. It may be localised or total in the scalp. The commonest type, which is hereditary, is male baldness (androgenic alopecia). Female balding spares the anterior hair line, develops later, and is less severe than the male variety. Diﬀuse hair loss is common after childbirth, severe illness or infection (telogen alopecia); it begins 8–12 weeks after the causative event and recovery is complete. Persistent diﬀuse hair loss may be caused by severe iron deﬁciency or HYPOTHYROIDISM, or may be drug-induced.
Patchy localised hair loss is commonly caused by fungal infections (tinea capitis – see RINGWORM), especially in the tropics. It may also be due to trauma, such as hair-pulling by children or disturbed adults, or hair-straightening by African or Afro-Caribbean women (traction alopecia). Rarely, diseases of the scalp-skin such as discoid lupus erythematosus (see under LUPUS) or lichen planus (see under LICHEN) may cause patchy alopecia with scarring which is irreversible. The long-term eﬀects of radiotherapy may be similar.
Treatment depends on the cause. Speciﬁc antifungal drugs cure tinea capitis. Correction of thyroid or iron deﬁciency may be dramatic. Male baldness may be modiﬁed slightly by long-term use of minoxidil lotion, or improved permanently by various types of hair-follicle grafting of transplants from the occipital scalp. Female balding may be amenable to anti-androgen/oestrogen regimens, but severe forms require a wig.