Perennial is more effective than preseasonal subcutaneous immunotherapy in the treatment of seasonal allergic rhinoconjunctivitis.

Background: Two different regimens of subcutaneous immunotherapy (IT), perennial or preseasonal, may be used in the treatment of seasonal allergy. The aim of this study was to compare the efficacy and safety of perennial IT (PIT) and preseasonal IT (PSIT) in patients suffering from seasonal rhinoconjunctivitis.

Methods: The study was planned as a randomized, double-blind, comparative study on the efficacy and safety of PIT and PSIT. The study group comprised 120 patients allergic to grass and rye pollen. After the observational season they were randomized to receive PIT or PSIT for 3 years. The effect of IT was assessed based on symptom severity and medication use recorded in diaries.

Results: Ninety-nine patients completed the study. No difference was seen between the groups regarding combined symptom medication score (SMS) in the first season of IT. During the second season, the difference between PIT and PSIT regarding combined SMS was 27.9% (p = 0.063) and reached 42.7% (p = 0.012) in favor of PIT in the third season. Both treatments had a similar safety profile.

Conclusion: PIT was more effective than PSIT in the treatment of rhinoconjunctivitis in patients allergic to grass and rye pollens.