A DOUBLE-BLIND, PLACEBO-CONTROLLED EVALUATION OF SUBLINGUAL IMMUNOTHERAPY WITH STANDARDIZED CAT EXTRACT

Background: In light of the controversial status of sublingual immunot herapy in patients with allergic rhinitis, we undertook a double-blind study of this form of treatment. Methods: Forty-one subjects with cat allergy presenting as rhinoconjunctivitis underwent 105 days of subli ngual immunotherapy, with 20 subjects receiving a standardized cat ext ract (total dose approximately 4,500, 000 allergy units) and 21 a matc hing placebo. Effectiveness of treatment was assessed by changes in sy mptoms and nasal-blockage index during 90 minutes of exposure in an ap artment containing cat dander, which was performed before and after th e course of treatment. Changes in cat-specific IgG and IgE levels and skin-test reactions were also monitored. Results: Although there were fewer symptoms and less nasal obstruction on cat dander exposure at th e end of the study the changes were not significantly different in tho se receiving active or placebo treatment. Specific IgG and IgE levels and prick skin test results did not change significantly during the co urse of the study. Conclusions: We conclude that sublingual immunother apy with high-dose standardized cat extract was no more effective than placebo in reducing symptoms or affecting immunologic measures of cat sensitivity.