Antihistamines: do they work? Further well-controlled trials involving larger samples are needed.

Histamine is one of the most important steps in the phlogistic allergic reaction. Its activity is due to the link to specific receptors on the cellular surface. H1-receptors of second generation are the most currently prescribed drugs in allergic diseases for their high selectivity, little or no central sedative effect, rapid onset of action and long half lives. Antihistamines can modulate part of immunological mechanisms involved in the pathogenesis of allergic inflammation reducing mediator release and expression of adhesion molecules, regulating the release of cytokines, chemokines and consequently inflammatory cells recruitment. The anti-inflammatory effects of cetirizine, desloratadine and levocetirizine are reviewed. Quality of life is considered too, as a main parameter in a global evaluation of the antihistamine's effects. Copyright 2004 Blackwell Munksgaard