Multiple daily administrations of low-dose sublingual immunotherapy in allergic rhinoconjunctivitis

Background: Sublingual immunotherapy (SLIT) is an efficacious treatment for allergic rhinoconjunctivitis. Objective: To investigate whether the number of daily administrations of SLIT can affect its efficacy. Methods: In an open study, 64 patients with allergic seasonal rhinoconjunctivitis to grass or birch pollens were assigned to the following 2-year daily treatment schedules: "3-3" group, 1 drop 3 times daily for 2 years; "2-3" group, 1 drop twice daily in year 1 and 1 drop 3 times daily in year 2; "1-3" group, 1 drop once daily in year 1 and 1 drop 3 times daily in year 2; and control group, no treatment. One fifth of the allergen concentration recommended by the manufacturer as maintenance treatment was used throughout the study. Patients were monitored for skin reactivity to the allergen used for SLIT using an end point dilution technique and for drug use. Results: No treatment-related adverse effects were observed. Skin reactivity to allergen decreased compared with controls in the first treatment year only in the "3-3" group and in all treated patients in year 2. Drug use decreased in the first treatment year in the "3-3" and "2-3" groups vs controls. This outcome extended to "1-3" patients in treatment year 2. Antihistamine use decreased significantly compared with baseline in year 1 in "3-3" and "2-3" patients and in all treated patients in year 2. No changes were observed in controls. Conclusion: The number of daily administrations seems to correlate with the efficacy of SLIT.