Three Consecutive Episodes of Thunderstorm Asthma in Ahvaz, Iran: the Possible Role of Conocarpus Pollen.

Background: The aim of this study is to evaluate the clinical pattern of thunderstorm asthma (TA) and the possible environmental hypotheses involved in the escalation of these epidemics. Materials and Methods: This retrospective descriptive study examined patients with respiratory problems referred to the clinics and emergency departments in Ahvaz, Iran during 2013-2016 periods following the first episodes of rainfall in autumn. The seasonal profile of airborne pollens and fungal spores in Ahvaz were characterized and clinical and spirometry findings of 443 patients were evaluated. Results: Of 56,000 people referred to the emergency department due to respiratory problems associated with the first rainfall in Khuzestan province, 91.4% displayed asthma-like symptoms and 71.3% had a history of allergic rhinitis. According to the results of spirometry test 38%, 52.9%, and 9.1% of patients had normal, obstructive, and restrictive patterns, respectively. Our results highlight the importance of allergic rhinitis as risk factors of TA epidemics. In terms of pollen, seasonal pollen integral was much higher in autumn than in winter. Conclusion: Our results highlight the importance of seasonal allergy and rhinitis as risk factors for thunderstorm asthma epidemics.