Full consideration of the pollen exposure effect in clinical trial design for pollen-induced allergic rhinitis

Allergic rhinitis (AR) is global health concern with an increasing prevalence. Among them, pollen-induced AR (PIAR) exhibits more severe and intense symptoms, decreased quality of life, prominent local inflammation, and is thus more challenging to control. Due to the difficulties in disease control, in recent years, an increasing number of treatment methods, including pharmacotherapy, allergen-specific immunotherapy, and newly developed biologics, have focused on PIAR. It has been shown that the pollen exposure has a significant impact on the symptoms of PIAR and the efficacy of intervention. From this perspective, clinical trials for PIAR need to take full account of pollen exposure, especially when assessing efficacy.

This review summarized the effect of pollen exposure on PIAR, including immune responses, symptoms and clinic visits. Current definitions for the pollen season (PS) and the peak pollen season (PPS) are discussed. Based on the previous PIAR-related clinical studies and the available recommendations for clinical trial design, a detailed account of trial protocols which fully considered pollen exposure is provided.

Pollen exposure has a significant impact on PIAR. With fully considering the pollen exposure in the clinical trial design for PIAR, future protocols for PIAR-related studies may be more objective and better harmonized and, therefore, comparable.