Non-specific hyperreactivity before and after nasal specific immunotherapy

Background: specific local immunotherapy (SLIT) improves symptom scores for allergic rhinitis during treatment and after its conclusion, as confirmed by non-specific tests. However, the duration of clinical and instrumental improvement after discontinuing SLIT is unknown. Objective: to evaluate the changes in the non-specific reaction time of patients with allergy to Dermatophagoides pteronissinus before and during 3 years of SLIT, and 6, 12, 18, and 24 months after discontinuing SLIT. Material and methods: sixteen patients were diagnosed by clinical history, positive skin test for D. pteronissinus, RAST, nasal provocation test (NPT) specific for D. pteronissinus, NPT with cold water solution. SLIT was administered by nasal spray. Patients were evaluated before, at 6, 12, 24, and 36 months of SLIT, and 6, 12, and 18 months after discontinuing SLIT. At the beginning of SLIT, the allergen concentration used was similar to that used in NPT. Maintenance doses were administered 3 times a week for 1 year and 2 times a week for 2 years. All patients kept a symptom diary. Results: after the first year of SLIT, total nasal resistance (TNR) decreased sharply. TNR then remained constant at the end of the second year and decreased at the end of the third year of treatment. Discontinuation of SLIT did not produce evident variations in average TNR at 6 or 12 months, but 3/16 patients at 6 months and 9/16 patients at 12 months complained of symptomatic deterioration. The most evident deterioration was noted at the 18-month post-SLIT visit, in which TNR values were similar to those recorded at the onset of treatment. Positive response to stimulation and increased TNR were found after SLIT in 8/16 patients at 6 months, 13/16 at 12 months, 12/13 at 18 months, and 7/7 at 24 months. The symptom score indicated the return of symptoms. Twelve months after discontinuing SLIT, the patients complained about increased secretion and itching. The initial non-specific hyperreactivity, which had been present in all patients, was not evident in 68.7% after 3 years of SLIT, but persisted in a milder form in 31.3%. Conclusion: SLIT successfully reduced symptoms of D. pteronissinus sensitivity. Non-specific hyperreactivity was absent at the end of SLIT, but returned by 6 months after discontinuing SLIT. Therefore, SLIT did not maintain the clinical results achieved at the beginning of treatment for more than 12 months.