ORIGINAL ARTICLE GASTROINTESTINAL DISEASES Seasonal distribution of initial diagnosis and clinical recrudescence of eosinophilic esophagitis: a systematic review and meta-analysis A. J. Lucendo 1 ,  A. Arias 2 , O. Redondo-Gonz alez 2 & J. Gonz alez-Cervera 3 1 Department of Gastroenterology, Hospital General de Tomelloso, Tomelloso; 2 Research Unit, Complejo Hospitalario La Mancha Centro, Alcazar de San Juan; 3 Department of Allergy, Hospital General de Tomelloso, Tomelloso, Spain To cite this article: Lucendo AJ, Arias  A, Redondo-Gonzalez O, Gonzalez-Cervera J. Seasonal distribution of initial diagnosis and clinical recrudescence of eosinophilic esophagitis: a systematic review and meta-analysis. Allergy 2015; 70: 1640–1650 Keywords eosinophilic esophagitis; meta-analysis; pol- len; season; systematic review. Correspondence Alfredo J Lucendo, MD, PhD, FEBGH, Department of Gastroenterology, Hospital General de Tomelloso, Vereda de Socu ellamos, s/n, 13700 Tomelloso, Ciudad Real, Spain Tel.: + 34 926 525 9267 Fax: + 34 926 525 870 E-mail: alucendo@vodafone.es Accepted for publication 14 September 2015 DOI:10.1111/all.12767 Edited by: Hans-Uwe Simon Abstract Background: The association between seasonality and diagnosis and/or recrudes- cence of eosinophilic esophagitis (EoE) remains unclear, with some studies demonstrating a higher diagnostic rate in those months with a higher aeroallergen load while others rule out this association. Methods: We performed a systematic search of the MEDLINE, EMBASE, and SCOPUS databases for studies on the seasonality of the initial diagnosis or recrude- scence (i.e., food bolus impaction) of EoE. Summary estimates, including 95% con- fidence intervals, were calculated for seasonal variation in diagnosis or incidence of food bolus impaction. A random-effects meta-regression model was made using aggregate-level data to compare seasonality in EoE diagnosis and recrudescence. Publication bias risks were assessed by means of funnel plot analysis. Results: Of 1078 references found, data were finally collected from 18 studies which included a total of 16 846 EoE patients. Of all new cases of EoE diagnosed per year, 27.1% were diagnosed in spring and 21.5% in winter. No overall statis- tical differences in the annual seasonal distribution of newly diagnosed EoE cases were observed in the random-effects meta-regression model (P = 0.132). Similarly, a homogenous distribution of episodes of EoE recrudescence throughout the year was noted, with no significant differences between seasons (P = 0.699). No signifi- cant publication bias was found. Conclusions: This systematic review found no significant variations in the sea- sonal distribution of either the diagnosis or clinical recrudescence of EoE throughout the year. Eosinophilic esophagitis (EoE) is a chronic immune-mediated inflammatory disorder, defined symptomatically by esopha- geal dysfunction and histologically by eosinophil-predomi- nant inflammation of the esophagus (1). Despite having first been characterized as a distinct clinicopathological disorder 20 years ago (2, 3), EoE has just recently become recognized as the most prevalent cause of chronic dysphagia among chil- dren and young adults (4–6). From its earliest descriptions, EoE has been linked to allergy; both pediatric and adult patients commonly present a personal medical and/or family history of atopic conditions such as asthma, rhinitis, conjunctivitis, eczema, and IgE-me- diated food allergies (1). Indeed, the presence of atopic manifestations in a patient who has been referred for esopha- geal symptoms (especially dysphagia or food impaction) has been recognized as a characteristic marker of EoE (7). Food sensitization identified through positive results in skin prick tests (SPTs) is also commonly described in patients of all ages (8, 9). The definitive categorization of EoE as a charac- teristic manifestation of food allergy came later, when researchers documented disease remission after feeding a ser- ies of pediatric patients exclusively with an amino acid-based elemental formula lacking any antigenic capacity, followed by disease recurrence after subjects resumed a normal diet (10). Since then, various dietary interventions have proven their efficacy in producing histologic remission in patients with EoE (11). However, such interventions are not always effective in inducing disease remission, with up to 10% of Allergy 70 (2015) 1640–1650 © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd 1640 Allergy