Long-term sublingual immunotherapy provides better effects for patients with Japanese cedar pollinosis.

Objective: Japanese cedar pollinosis is an endemic disease affecting a large proportion of Japan's population. Five seasons have passed since sublingual immunotherapy (SLIT) for Japanese cedar pollinosis was included in the public insurance coverage in Japan. In this study, we evaluated the clinical effects of long-term SLIT for Japanese cedar pollinosis on upper respiratory symptoms primarily represented by nasal symptoms and inflammation of the respiratory tract in the 2019 season, in which considerable amount of cedar pollen was dispersed.

Methods: This study involved 95 patients who were undergoing SLIT for Japanese cedar pollinosis after the initiation at some point between 2014 and 2018, and this group of patients was compared with a control group comprising 21 patients receiving preseasonal prophylactic treatment (with a second-generation antihistaminic drug). We evaluated the patients' nasal/eye symptoms, total nasal symptom and medication score (TNSMS), and quality of life according to relevant guidelines. In addition, the levels of peripheral blood eosinophils, serum total IgE, Japanese cedar antigen-specific IgE, Cryj1-specific IgG4, and fractional exhaled nitric oxide (FENO) were measured as objective indices.

Results: From the fourth season (SLIT4), nasal discharge, sneezing, nasal obstruction symptoms, and TNSMS significantly decreased compared with those in the preseasonal prophylactic treatment and SLIT1 groups. In the patients suspected to have eosinophilic airway inflammation (with a baseline FENO ≥25 ppb), the interannual variability of FENO levels significantly reduced after 5 years of treatment.

Conclusion: The efficacy of SLIT was noted from the first year of treatment, even in a year when pollen profusely dispersed. Thus, long-term continuous treatment with SLIT may alleviate nasal symptoms as well as eosinophilic airway inflammation.