Long-term effects of allergen sublingual immunotherapy

Introduction
Allergen-specific immunotherapy (AIT) is a crucial therapy for allergic rhinitis. However, the long-term effectiveness of AIT remains to be explored.

Aim
To evaluate clinical and immunological long-term effects of sublingual allergen immunotherapy (SLIT) for common inhalant allergens in elderly patients with allergic rhinitis.

Material and methods
This trial was a prospective follow-up observation of patients with allergic rhinitis who completed SLIT for grass pollen or house dust mites (HDM). After 3 years of SLIT, 115 patients were compared to a placebo group during an additional 5 years of observation. The combined symptom medication score (SMS), quality of life and concentration of IgG4 for Phleum pratense or Dermatophagoides pteronyssinus were monitored during the study.

Results
Five years after SLIT was discontinued, a significant clinical effect based on SMS was still observed compared with the baseline, just after SLIT and 5 years later as follows: 7.53 ±2.09 vs. 2.45 ±0.72 vs. 3.09 ±1.07 (p < 0.05) for HDM and 8.19 ±2.41 vs. 3.05 ±1.62 vs. 4.47 ±2.31 (p < 0.05) for grass pollen. Quality of life based on the Rhinoconjunctivitis Quality of Life Questionnaire was significantly improved in patients who received SLIT and remained at a good level after 5 years of observation. During the 5 years of observation after SLIT, there were no significant changes between specific IgG4 levels and the analysed allergens compared to results just after SLIT.

Conclusions
The positive effect obtained after SLIT for grass pollen or house dust mites was sustained for a long period after AIT.