Background: The fast-dissolving grass allergy immunotherapy tablet (grass AIT), Grazax, has proven effective in grass pollen–induced rhinoconjunctivitis.
Objective: To investigate the immunological and cutaneous changes induced after a short course with grass AIT.

Methods: We performed a randomized, double-blind placebo-controlled trial with 78 patients randomly assigned to receive either grass AIT or placebo in a 2:1 ratio. Treatment lasted at least 8 weeks before the grass pollen season (GPS), and continued until the seasonfinished. Specifi c immunoglobulin (Ig) G4, IgE, and IgE-blocking factor to Phleum pratense were measured at the beginning of the trial and at different intervals during treatment. Immediate and delayed skin tests with P pratense were also performed. Safety endpoints were defined in terms of adverse events reported.

Results: A total of 75 patients completed the trial (50 active and 25 placebo). P pratense IgG4, IgE, and IgE-blocking factor in actively treated patients increased significantly from baseline to the start of the GPS compared to placebo (P>.001, P=.017, and P=.005, respectively). The immediate cutaneous response was reduced during therapy in actively treated subjects, whereas placebo-treated subjects showed a decrease only after the start of the GPS. The delayed response to the intradermal test in grass AIT–treated subjects diminished, although not in a significantly different way from the placebo-treated subjects.

Conclusion: Treatment with grass AIT for grass pollen allergic rhinoconjunctivitis induces immunological changes after only 1 month of treatment.

Key words: Grass pollen allergy. Grass allergy immunotherapy tablet. Immunological changes. Sublingual immunotherapy.