The humoral IgA is an immunoglobulin which plays a defensive role for organisms on mucosal surfaces. Today, intranasal antihistamines are effectively used in the treatment of allergic rhinitis. In our study, the effect of azelastine hydrochloride-a nasal antihistaminic-on humoral IgA of the nasal mucosa has been reviewed empirically. Twenty-four female Sprague-Dawley rats were included in our study. The rats were divided into three groups randomly. Group 1(azelastine hydrochloride): rats in this group had nasal azelastine hydrochloride (0.05%) applied for 30 days at 10 A mu l/nostril dosage. Group 2 (saline): saline (0.09%) was applied to the rats in this group for 30 days at 10 A mu l/nostril dosage. Group 3 (control): no application was made throughout the study. The chemicals applied in Groups 1 and 2 were applied to both nostrils by mounting a flexible micropipette to the end of an insulin injector. At the beginning of the study, nasal lavage was performed to both nostrils of the rats in every group on the 15th and 30th day to aspirate irrigation solution (distilled water). The aspirated liquids were kept at - 80A degrees temperature and reviewed together at the end of study. Within-group comparisons: in Group 1 (azelastine hydrochloride), the humoral IgA value on the 15th day was significantly higher than the basal value (p = 0.037). There is a significant difference between humoral IgA value on the 30th day and humoral IgA value on the 15th day (p = 0.045). In Group 2 (saline), no significant difference is available between basal, 15th day and 30th day humoral IgA values (p = 0.265). In Group 3 (control), no significant difference is available between basal, 15th day and 30th day humoral IgA values (p = 0.374). Between-group comparison: there is no significant difference in between-group humoral IgA basal values (p = 0.714). On days 15 and 30, Humoral IgA value of Group 1 was significantly higher than that of Groups 2 and 3 (p = 0.013, p = 0.024, respectively). According to the results we achieved in our study, nasal antihistaminic (azelastine hydrochloride) significantly increases the level of humoral IgA. Our study is the first one in the literature to reveal a relation between nasal antihistaminic and humoral IgA and there is a further need for clinical, randomized and prospective studies.