Objective ·To explore the clinical features of allergy-related obstructive parotitis (AROP) and the ultrasonic characteristics of its duct. Methods ·Patients diagnosed with AROP at the Oral Surgery Department of Shanghai Ninth People′s Hospital, Shanghai Jiao Tong University School of Medicine from October 2020 to October 2022 due to recurrent swelling of parotid gland were included. Clinical data of the patients were retrospectively analyzed, including medical history, clinical manifestations, laboratory examinations and imaging examinations. Static ultrasound was used to display the morphological characteristics of the AROP duct, ultrasonic images were used to measure the inner diameter at the widest point of duct dilation, and the degree of duct dilation was graded. Dynamic ultrasound was used to show the morphological changes of the duct at the functional state of AROP patients. The value and ratio of duct widening were calculated, and the symptoms of parotid swelling were recorded. Results ·Thirty-seven patients were diagnosed with AROP and included in the study, including 9 males (24.3%) and 28 females (75.7%). The main clinical symptoms were recurrent swelling of parotid gland, skin itching and duct discharge of mucus plug. Thirty-two patients (86.5%) had a history of systemic allergic disease. The proportion of increased serum IgE concentration and peripheral blood eosinophil (PBE) absolute count was 59.5% and 43.2%, respectively. The static ultrasound results of 37 AROP patients were mainly manifested by duct dilation. The grading results of duct dilation degree were mild in 21 cases (56.8%), moderate in 10 cases (27.0%) and severe in 6 cases (16.2%). Seven patients with AROP underwent dynamic ultrasonography. Results showed that 4 patients were in the asymptomatic period and 3 patients were in the symptomatic period. Conclusion ·AROP is a type of chronic obstructive parotitis closely related to allergic reactions, and its diagnosis should be considered in many aspects. Ultrasound can effectively display the morphological characteristics of parotid duct, and can be used to assess the obstruction status of the duct, which is helpful for the diagnosis and follow-up of AROP.