Clinical and immunologic effects of long-term sublingual immunotherapy in asthmatic children sensitized to mites: a double-blind, placebo-controlled study

Background: Immunotherapy through local routes is thought to be a valuable therapeutic option for respiratory allergy. We investigated the clinical efficacy and immunologic effects of sublingual immunotherapy (SLIT) in asthmatic children with mite-induced respiratory allergy. Methods: Twenty-four patients (age range 8-15 years), suffering from mild to moderate asthma, with single sensitization to mite allergen, were enrolled. After a 1-year observation phase, patients were randomly allocated to one of two groups, and were given SLIT (sublingual-spit) as drops for 2 years according to a double-blind, placebo-controlled (DBPC) design. Symptoms/medication scores (diary card), visual analog scale, and immunologic parameters (house-dust-mite [HDM]-specific IgE, and total HDM-specific IgG and IgG4) were determined during the observation phase and during the DBPC treatment period. Results: Twenty-one patients completed the study. At the beginning of the treatment, no difference in environmental allergenic pressure could be shown between the groups. After 2 years of therapy, there was a significant decrease ill asthmatic symptoms (P = 0.0001) and medication use (P = 0.0001) in the active group compared to the placebo group. The visual analog score on overall asthma symptoms improved in the SLIT group (P = 0.0001), but not in the placebo group. Nevertheless, the immunologic results did not show significant differences in HDM-specific IgE and total HDM-specific IgG or IgG4 between the active and placebo groups (P = NS). No relevant side-effects were recorded throughout the study. Conclusions: Our results suggest that treatment for 2 years with SLIT is clinically safe and effective in significantly decreasing respiratory symptoms in children with mild to moderate asthma sensitized to HDM. On the other hand, the lack of changes of the immunologic parameters calls for further investigations with special reference to kinetics and mechanism(s) of action of this mode of treatment.