Oral allergy syndrome (OAS) is characterized by an immediate allergic reaction that mainly or partially affects the oral mucosa, pharynx, or lips, and it is usually caused by ingesting fresh fruits or vegetables. Most patients with OAS also have allergic rhinitis due to pollen. As allergic rhinitis is increasingly prevalent in the Japanese population and the age at disease development is decreasing, morbidity associated with OAS among the younger population is likely to increase. However, there is little information about the prevalence of this disease among Japanese children, specifically the influences of residency in regions with different environments.