Intradermal Phleum pratense allergoid immunotherapy. Double-blind, randomized, placebo-controlled trial.

Background: In allergology, the intradermal approach is generally used to establish an aetiological diagnosis, with limited experience in specific allergen immunotherapy.

Objective: To evaluate the efficacy and safety of immunotherapy with an allergen extract of glutaraldehyde-polymerized Phleum pratense, administered intradermally, in patients with rhinoconjunctivitis sensitized to grass pollen.

Methods: Multicentre, randomized, double-blind, placebo-controlled clinical trial in patients from 12 to 65 years of age with rhinitis or rhinoconjunctivitis, with or without asthma, due to grass pollen allergy. Patients were divided into three groups and received a total of six doses in a weekly interval, of either placebo; 0.03 or 0.06 μg of protein per dose of P pratense allergoid. The primary objective was to evaluate the combined symptoms and medication consumption score (CSMS). The secondary objectives were symptoms and medication, tolerance to the conjunctival provocation test, specific IgE and IgG4 antibodies and the safety profile according to the WAO scale.

Results: The dose of 0.06 μg of protein proved to be effective versus the placebo by significantly reducing CSMS and increasing tolerance to the allergenic extract in the conjunctival provocation test, after the first pollen season. This group showed a significant reduction in specific IgE after the second pollen season relative to the baseline. There were no variations in IgG4 levels. Only one grade 2 systemic reaction was recorded.

Conclusion & Clinical Relevance: Intradermal immunotherapy with P pratense allergoid has been shown to be effective and safe, reducing CSMS, increasing tolerance to the conjunctival provocation test and reducing IgE levels.