Treatment of perennial rhinitis, seasonal allergic rhinitis, chronic idiopathic urticaria, allergic conjunctivitis, and other forms of allergy. In addition to its increased potency as H1 antagonist, Cetirizine is also classified as a non-sedating antihistamine. Cetirizine dihydrochloride has a role in both skin and nasal allergic reactions with particular emphasis for its potential for inhibiting the Late Phase Response (LPR). CETIRIZINE apparently reduces allergic inflammation and cellular influx by mechanisms other than H1 blockade. CETIRIZINE also inhibits the delayed reactions observed after injection of platelet activating factor 9AFP, kalikrein and serum and PAF-induced eosinophil chemostaxis. In addition to its inhibiting effect on allergic skin reaction, CETIRIZINE also has an effect on the nasal allergic response. A significant reduction in sneezing and the amount of recovered albumn tame esterase activity and leukotriene C4 was observed.