The purpose of this study was to characterize the late phase nasal obstruction that is induced by a nasal histamine challenge in sensitized guinea pigs. The volume of the nasal cavity was measured using an acoustic rhinometer. A nasal histamine challenge to unsensitized animals induced nasal obstruction at 30 minutes after the challenge while a challenge to sensitized animals induced nasal obstruction not only at 30 minutes but also at 4-6 hours. Histamine (measured by high-performance liquid chromatography), cysteinyl leukotriene (enzyme-linked immunosorbent assay (ELISA)), prostaglandin D2 (ELISA), eosinophils and basophilic cells of sensitized guinea pigs were not changed in the late phase after histamine challenge. Administration of pyrilamine, a histamine H1 receptor antagonist, and calcitonin gene-related peptide (CGRP) (8-37), a CGRP-1 receptor antagonist, significantly improved histamine-induced nasal obstruction at 30 minutes and in the late phase, respectively. These results suggest that a nasal histamine challenge induces nasal obstruction not only immediately through the histamine H1 receptors but also in a late phase via CGRP.