House-dust-mite sublingual-swallow immunotherapy (SLIT) in perennial rhinitis: a double-blind, placebo-controlled study

Background: The safety and efficacy of sublingual-swallow immunotherapy (SL IT) in rhinitis caused by house-dust mite were evaluated in a double-blind, placebo-controlled study including 75 patients for 24 months. Methods: Patients received either placebo or SLIT with a standardized Derma tophagoides pteronyssinus (D.pt.) - D. farinae (D.f.) 50/50 extract. The me an cumulative dose was 90 000 IR, equivalent to 2.2 mg of Der p 1 and 1.7 m g of Der f I. Symptom and medication scores were assessed throughout the st udy. Exposure to house-dust mite, skin sensitivity, and serum specific IgE and IgG4 were assessed before starting treatment and after 12 and 24 months . Results: Seventy-two patients (36 active-36 placebo) were eligible for inte nt-to-treat analysis. Thirty-six patients dropped out of the study. The num ber of patients who dropped out due to lack of efficacy was eight out of 37 (21.6%) in the active treatment group compared to 15 out of 38 (39.5%) in the placebo group (chi-square = 2.81, P = 0.09). Total symptom and medicati on scores decreased significantly after 12 and 24 months (P < 0.05) of trea tment in both groups, but no significant difference was observed between th e active and placebo groups. After 24 months, the number of patients with h igh levels of indoor allergenic load decreased significantly in both groups compared to baseline data (P = 0.01). Specific IgE (D.pt. and D.f.) increa sed significantly in the active treatment group after 12 and 24 months, whi le no change was observed in the placebo group. Specific IgG4 levels were n ot significantly modified in either group. Two patients in each group repor ted mild adverse effects. No severe adverse effects were reported. Conclusions: We conclude that SLIT in rhinitis caused by house-dust mite wa s safe, but there was a lack of consistent clinical benefit compared to pla cebo, probably due to the impact of the allergen avoidance measures that lo wered the allergen burden.