Cetirizine is a second-generation antihistamine that effectively treats allergic rhinitis, such as hay fever, by blocking peripheral H1 receptors to relieve symptoms like sneezing, runny nose, and itchy eyes. It is also indicated for chronic idiopathic urticaria, reducing the occurrence, severity, and duration of hives while exhibiting anti-inflammatory properties that inhibit eosinophil chemotaxis and cytokine release. As the active metabolite of hydroxyzine, cetirizine works selectively without significant central nervous system penetration, distinguishing it from first-generation antihistamines.