Unveiling the Impact of Smoking on Allergic Rhinitis: Disease Severity and Efficacy of Subcutaneous Immunotherapy.

Objective: To evaluate the impact of smoking statuses on disease severity and subcutaneous immunotherapy (SCIT) efficacy in allergic rhinitis (AR).

Study design: Open observational cohort study.

Setting: Tertiary referral center.

Methods: Five hundred and five AR patients undergoing dust mite allergen SCIT were categorized into never smokers, former smokers, and current smokers. AR severity was assessed using widely employed questionnaires. The changes in questionnaire scores pre- and post-SCIT were evaluated for SCIT efficacy. The differences in disease severity and SCIT efficacy were compared for different smoking statuses among AR patients.

Results: Compared to never smokers, former and current smokers exhibited higher proportion of male, alcohol, and asthma (P < .05). Current smokers had a greater prevalence of allergic conjunctivitis than former smokers (P < .05). Before SCIT, AR severity was similar across 3 groups, even after adjusting for confounders (P > .05). Current smokers reported lower SCIT efficacy in the first year (P < .05). By the third year, 3 groups showed comparable long-term efficacy (P > .05). However, current smokers experienced a significant decrease in benefits 2 years post-SCIT (P < .05) and lower improvement rates at the end of the 3-years SCIT period and 2 years following SCIT (P < .05).

Conclusion: AR patients across different smoking statuses demonstrated similar baseline disease severity and long-time SCIT efficacy. Active smoking was associated with increased asthma risk, delayed early SCIT efficacy perception, reduced improvement over 3 years, and diminished benefits 2 years after SCIT. Prompt smoking cessation is crucial to mitigate these effects.