Background: Kimura disease (KD) is a rare, chronic inflammatory disorder characterized by blood eosinophilia, general itching, and subcutaneous head and neck mass lesions; however, the etiology of this disease is unknown. We hypothesized that group 2 innate lymphoid cells (ILC2s) in peripheral blood may play an essential role in the pathogenesis of KD. Methods: The prevalence of blood ILC2s and their ability to produce interleukin (IL) -4, IL-5, IL-13, and IL-31 in patients with KD were compared with those in control subjects and in patients with house dust mite (HDM) -induced allergic rhinitis (AR). Changes in blood ILC2 prevalence, blood eosinophilia, and clinical symptoms after surgery and steroid therapy were evaluated. Results: Blood ILC2 prevalence in patients with KD were eight times and six times higher than those in control subjects and in patients with AR, respectively. There was a strong positive correlation between ILC2 prevalence and blood eosinophilia. Patients with KD showed increased serum IL-13 and decreased IL-31 levels. KD patient-derived blood ILC2s produced large amounts of IL-5 and IL-13 in response to prostaglandin (PG) D ₂ and leukotriene (LT) D ₄, compared to ILC2s derived from control subjects and patients with AR. Surgery and systemic steroid therapy ameliorated general itching with a concomitant decrease in blood ILC2s and blood eosinophilia. Upon disease recurrence, blood ILC2 prevalence and blood eosinophilia increased concurrently with general itching. Conclusion: Increased blood ILC2s may be involved in blood eosinophilia and general itching through the production of IL-5 and IL-13 in patients with KD.