Drug reactions affecting hair: diagnosis.

Drugs may cause hair loss, stimulate hair growth, or induce changes in the hair shape and color. Drug-induced hair loss is, in most cases, a consequence of a toxic effect of the drug on the hair matrix. Although a large number of drugs have been occasionally reported to produce hair loss, the relationship between drug intake and hair loss has been proven only for a few agents. Type of hair loss (telogen effluvium, anagen effluvium, or both) depends on the drug, its dosage, and patient's susceptibility. Drug-induced hair loss is usually reversible.