Background: Allergic rhinitis (AR), the most prevalent allergic disease, has a rising trend in the world and has significantly impaired the quality of life of the patients. Aeroallergens are the major cause of allergic rhinitis and among them pollens are the main allergens responsible for allergic rhinitis in

Iran. There is a little information about the role of different pollens in allergic rhinitis, in our country. Therefore, this study was conducted to determine the prevalence of allergy to autumn pollens in allergic rhinitis patients.

Methods:�In this retrospective cross-sectional study, the medical records of 245 allergic rhinitis patients referred to Immunology-allergy clinic of

Hazrat

Rasool-e-Akram

Hospital in

Tehran during 2005-06 were assessed. Required information about allergic rhinitis sign and symptoms, laboratory data (total serum Ig E level and eosinophilia in nose smear) and Skin Prick Test (SPT) results for autumn pollens were obtained from the medical records of each patient. Finally, data were analyzed using SPSS V.14 software and Chi² and Mann-Whitney U tests were performed in analysis.

Results:�Out of 245 allergic rhinitis patients, 238 patients (97.1%) had positive skin prick test for at least one aeroallergen and the prevalence of allergy to autumn pollens (weeds) was 87.3% (214 cases). Among autumn pollens, Lamb’s Quarter caused the most positive skin prick test (74.7%). Moreover, nasal smear eosinophilia was present in 35.9% of patients and the mean of total serum Ig E level was 219.06 IU/mLit. There was no statistical difference in the prevalence of allergy to these pollens between two sexes whereas, adults had significantly higher rates of allergy to autumn pollens (89.6% versus 73.5%, p=0.009).