Rational use of antihistamines in allergic dermatological conditions.

For many years, the use of antihistamines in dermatological conditions has been closely linked to the treatment of urticarias and to the symptomatic relief of pruritus. H1-receptor antagonists are the first-line drugs for urticarias. Those urticarias of type I immunological origin respond better than physical urticarias. H2-receptor antagonists may be added for refractory patients but are rarely effective alone. Conventional H1-blockers are frequently associated with somnolence and anticholinergic effects. Therefore, new antihistamines without depressive effects on the central nervous system have recently been introduced. In other pruritic conditions such as atopic dermatitis the limited effects of these drugs suggest that histamine is not the only mediator involved in pruritus. In these cases, their beneficial effects seem to be due mainly to their sedative properties; recently available nonsedative H1-blockers are less effective.