Levocabastine is a selective histamine H1-receptor antagonist exerting inhibitory effects on the release of chemical mediators from mast cells and on the chemotaxis of polymorphonuclear leukocytes and eosinophils. Both histamine and antigens induced conjunctivitis was inhibited by levocabastine in several allergy models. Levocabastine moderately inhibited histamine-release from guinea pig conjunctive induced by antigen-antibody reactions and prevented an increase in the vascular permeability of the conjunctive elicited by both histamine and antigen instillation. Symptoms of allergic rhinitis, which were induced by histamine, substance P and antigen, were also reduced by levocabastine. Levocabastine prevented an increase in the vascular permeability of nasal mucosa elicited by instillation of these three inducers. Furthermore, levocabastine has shown a large difference between the antiallergic dose and other non-specific pharmacological effective dose than that with other antiallergic drugs. The non-specific pharmacological effect of levocabastine reveals only blepharoptosis. With these pharmacological effects and topical usage, levocabastine was shown to be useful for allergic conjunctive and rhinitis in both seasonal and perennial clinical use.