2025/12/03 by Ayumi Shimamura, Reiji Kojima, Hiroki Ishii +3 · 1 voice
Medicine · #Allergic Rhinitis and Sensitization #Contact Dermatitis and Allergies #Food Allergy and Anaphylaxis Research
paper · pdf · doi:10.1111/all.70177
openalex publication_date 2025/12/03 · openalex created_date 2025/12/04 · openalex updated_date 2026/07/27
The prevalence and risk factors of oral allergy syndrome (OAS) [1], caused by loquat, a fruit of the Rosaceae family, remain unclear. In June 2024, raw loquat fruits were served in Yamanashi school lunches, after which many students developed OAS symptoms; some had systemic reactions. This prompted an epidemiological investigation to determine the prevalence of loquat allergy and its associated risk factors among elementary and middle school students. A web-based survey was conducted in November 2024, with responses from parents of 2360 children out of 3192 who were served loquat during school lunch. No exclusions were applied. Loquat-induced OAS was defined as itching or swelling of the oral or pharyngeal mucosa or lips within 15 min of consumption. Associations between loquat-induced OAS and a history of OAS from other foods or pollen antigen sensitization were examined using multivariate analysis. Among the 1768 children who reported consuming loquat, 264 (14.9%, 95% confidence interval: 13.3%–16.7%) developed OAS symptoms (Figure S1), and 67 (3.8%) exhibited non-oral symptoms. The prevalence of loquat-induced OAS was 10.0% (62/621), 20.1% (133/661), and 14.2% (69/486) in lower elementary, upper elementary, and middle school students, respectively, with significant differences observed between adjacent grades. A similar pattern was observed for non-oral symptoms (Table S1). Overall, 407 of 2360 children (17.2%) had a prior OAS history (Table S1), most commonly due to Rosaceae foods (206/407, 50.6%) (Figure S2). Seasonal allergic rhinitis (sAR) prevalence was 75.8% (1790/2360 children) (Table S1), with Japanese cedar and cypress showing the highest sensitization rates (683/823, 83.0%) (Table S2). Children with loquat-induced OAS more often had a history of OAS (114/264, 43.2%) and sAR (240/264, 90.9%) than those without loquat-induced OAS (173/1504, 11.5% and 1086/1504, 72.2%, respectively) (Figure S3A, S3B). The difference was particularly pronounced for Rosaceae food-related OAS history (83/114, 72.8% vs. 52/173, 30.1%) (Table S3). Additionally, loquat-induced OAS was most prevalent in children sensitized to Fagales pollen (45/116, 38.8%) (Table S4). Multivariate logistic regression adjusted for grade and sex showed significant associations between loquat-induced OAS and a history of OAS from Rosaceae or Cucurbitaceae foods (Table 1). Sensitization to Fagales and grass pollen was also significantly associated with loquat-induced OAS (Table 2). Detailed procedures and statistical analyses are provided in the Supporting Information (Table S5, Figure S4). Bet v 1 homologs are suspected to be allergenic components of loquat; however, they have not yet been identified [2]. Our findings suggest that loquat-induced OAS represents a pollen-food allergy syndrome (PFAS) involving Bet v 1 homologs, such as PFAS caused by high antigenic similarity with other Rosaceae foods and Fagales pollen. Further research into the possible involvement of profilin, a minor allergen in Rosaceae food-induced PFAS, is warranted. Among children with loquat-induced non-oral symptoms, some had also experienced systemic reactions to other fruits, suggesting the involvement of gibberellin-regulated and lipid transfer proteins [1], which are known to cause relatively severe symptoms. Yamanashi Prefecture has one of the highest prevalences of sAR in Japan [3], and is characterized by high rates of alder pollen sensitization and Rosaceae fruit-induced PFAS [4]. However, our previous surveys revealed that only 40% of patients with oral allergy symptoms were aware of OAS [5]. Moreover, current Japanese school lunch guidelines do not list fruits as a food requiring special caution. In this context, 229 of 264 affected students (86.7%) had their first opportunity to eat loquats through the school lunch program, reflecting its limited distribution. This study has some limitations, including potential selection and recall biases, possible inaccuracies in self-reported blood test results, and unmeasured non-pollen causes of OAS. Additionally, clinical confirmation of loquat allergy was not feasible, and the study was conducted in a single municipality, which may affect the generalizability of the findings. Further studies in other regions are warranted. In conclusion, we analyzed the prevalence and associated risk factors of loquat allergy among school students. Our findings may help elucidate the pathogenesis of loquat allergy and highlight the importance of incorporating regional characteristics into patient education on PFAS [6]. These findings highlight the need for practical guidance to help patients understand regional PFAS risks, identify high-risk foods, and promote appropriate avoidance strategies. A.S., T.M., and D.S. conceived and designed the study. A.S., R.K., H.Is., T.M., H.Ik., and D.S. contributed to the study design and data collection. A.S., R.K., and D.S. performed the data analysis and interpretation and drafted and revised the manuscript. H.Is., T.M., and H.Ik. provided important intellectual input to the work. All authors reviewed and approved the final manuscript and agree to be accountable for all aspects of the work. We express our gratitude to all the participants of this survey and the educational, medical, and administrative officials of Yamanashi Prefecture and the relevant local governments. We would like to thank Editage (www.editage.jp) for the English language editing. This work was conducted with partial support from the Gender Equality Office University of Yamanashi. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. The authors declare no conflicts of interest. The data that support the findings of this study are available from the corresponding author upon reasonable request. Figure S1: Oral allergy syndrome (OAS) symptoms induced by loquat and corresponding medical visits. Figure S2: Foods previously associated with oral allergy syndrome (OAS), categorized by phytochemical class (common foods only). Figure S3: Comparison of children with and without loquat-induced oral allergy syndrome (OAS). Figure S4: Flowchart of participants included in the analysis. sAR, specific allergic rhinitis. Table S1: Characteristics of the study participants. Table S2: Prevalence of pollen-specific IgE antibody positivity by school grade. Table S3: Foods reported to have caused OAS in the past. Table S4: Prevalence of OAS stratified by pollen-specific IgE antibodies. Table S5: Characteristics of children who reported loquat consumption with seasonal allergic rhinitis. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.