[Adverse drug reactions on hair]

Adverse drug reactions on the hair are common side effects. The spectrum of loss of hair reaches from diffuse telogen effluvium up to circumscribed or diffuse alopecia on the scalp, sometimes also including other body areas. Other side effects observed are the stimulation of hair growth with hypertrichosis and induction or worsening of hirsutism, as well as changes of the structure or color of the hair. In most cases--other than those treated with cytostatics, androgens, or hormonal contraceptives with some androgenic effect--it is rather difficult to determine the time of onset and primary cause, since the diffuse types often start subclinically, and other factors may play an additional part. As a rule, adverse drug reactions are reversible provided the causative drug is avoided.