Background The safety and the efficacy of sublingual-swallow immunotherapy (SLIT) in perennial conjunctivitis caused by house dust mite were evaluated in a double-blind, placebo-controlled study including 60 patients for 24 months.
Methods Patients received either placebo or SLIT with standardized Dermatophagoides pteronyssinus (D.pt.) and D. farinae (D.f.) 50/50 extract. The evaluation of the efficacy of the SLIT was obtained by using standardized D. pteronyssinus (D.pt.) extracts on the antigen-specific conjunctival provocation test (CPT). Specific CPT, skin sensitivity and serum-specific IgE were performed before starting treatment and 6, 12, 18 and 24 months.
Results Of the 60 patients included, only 45 completed the study (26 in the active group and 19 in the placebo group, P < 0.05). Two out of 30 (6.6%) patients dropped out because of insufficient efficacy in the active group compared to eight out of 30 (26.6%) in the placebo group (P < 0.05). There was a significant increase in the antigen threshold required to obtain a positive CPT from 8.2 IR [95% confidence interval (CI) 5.9–11.4] at baseline to 21.7 IR (95% CI 15.4–30.4) at 2 years (M24) in the active group, compared to 8.1 IR (95% CI 5.4–12.1) at baseline to 8.1 IR (95% CI 5.1–12.4) at M24 in the placebo group (P < 0.04 for overall treatment difference, P < 10−7 for the time–treatment interaction; repeated measures ANOVA). Differences between groups at individual time points were significant from 18 months on. Despite increased antigen concentrations, CPT scores were lower overall in the active than in the placebo group (P < 0.001). No serious adverse effects were reported.
Conclusion SLIT effectively increased the antigenic threshold required to obtain a positive CPT to house-dust mite antigen. Tolerance to and innocuity of SLIT were comparable to previous studies. This could justify recommending SLIT for the preventive treatment of perennial conjunctivitis caused by house dust mites.