Objectives: In this study, we examined the effect of botulinum toxin A (BTA) on chronic allergic rhinitis (CAR). We tested the effects of BTA, applied to an intranasal sponge, on patients who had CAR for a minimum of three years and had been treated unsuccessfully with conventional medications.Method: The study was an interventional case-control single-blind randomized clinical trial. Forty-four male and female CAR patients who were referred to Tehran’s Saee & Pasargad Hospitals, and Saadat-Abaad, Sarv and Karimkhan Clinics in 2012; aged 20-40 years were selected on the basis of inclusion and exclusion criteria. The subjects were randomly assigned to the intervention (n=22) or control group (n=22).The intervention group received BTA (100 IU/ml; Dysport), on a 5cm nasal sponge retained in each nasal cavity for 30 minutes. The control group received normal saline. The groups were evaluated by the same examiner. Pre- and post-tests (1, 3, 6, and 12 weeks) were performed according to the authors’ pre-designed checklist, the validity and reliability of which was previously established.The symptoms scored from none (0) to severe (10) at the test points. The statistical analysis was conducted with SPSS-19, with a significance level of 0.05.Results: Based on ANOVA, there was a significant difference (P<0.05) in symptomatic relief between the intervention and control groups. No marked adverse effects were observed during the study.Discussion: An intranasal 5cm sponge impregnated with 100 IU/ml BTA, retained in each nasal cavity for 30 minutes, may alleviate CAR symptoms with no significant adverse effects.