Background: In light of the controversial status of sublingual immunotherapy 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 sublingual immunotherapy, with 20 subjects receiving a standardized cat extract (total dose approximately 4,500,000 allergy units) and 21 a matching placebo. Effectiveness of treatment was assessed by changes in symptoms and nasal-blockage index during 90 minutes of exposure in an apartment containing cat dander, which was performed before and after the 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 the end of the study the changes were not significantly different in those receiving active or placebo treatment. Specific IgG and IgE levels and prick skin test results did not change significantly during the course of the study.
Conclusions: We conclude that sublingual immunotherapy with high-dose standardized cat extract was no more effective than placebo in reducing symptoms or affecting immunologic measures of cat sensitivity.