Associations between dual use of combustible cigarettes and electronic nicotine delivery systems and allergic rhinitis: An analysis of KNHANES data

Background The dual use of combustible cigarettes (CC) and electronic nicotine delivery systems (ENDS) is a rapidly growing public health concern, yet its synergistic impact on allergic rhinitis (AR) remains poorly understood. Previous studies have reported inconsistent associations between smoking and AR, often failing to account for different tobacco product combinations and the temporal sequence of smoking initiation. Objective To analyze the association between diverse smoking behaviors—including exclusive CC use, exclusive ENDS use, and dual use—and the odds of AR diagnosis among Korean adults. Methods We analyzed data from 18,781 adults from the 2019–2022 KNHANES. Multivariable survey-weighted logistic regression estimated adjusted odds ratios (AOR) across 5 patterns: never, former, exclusive CC, exclusive ENDS, and dual users. Sensitivity analyses were conducted to establish temporal precedence by restricting the sample to those who initiated smoking prior to their AR diagnosis. Further stratified analyses were performed based on smoking intensity (Cigarettes Per Day [CPD]). Results The overall weighted prevalence of AR was 17.77%. In the primary model, exclusive CC smokers showed lower odds of AR (AOR = 0.691; 95% CI=0.562–0.850), which decreased further to 0.519 (p < 0.001) upon temporal validation. While the primary model showed higher odds for former smokers (AOR = 1.193), the validated subset revealed a significant inverse association (AOR = 0.836, p=0.018), identifying a "sick quitter" effect. Conversely, dual use of CC and vapes was significantly associated with higher AR odds (AOR = 1.543; 95% CI=1.067–2.233, p=0.021). This risk peaked among moderate smokers using vapes (AOR = 2.222, p=0.029) and heavy smokers using heated tobacco products (AOR = 2.374; 95% CI=1.059–5.322, p=0.036). Conclusion Our findings reveal a distinct contrast between exclusive smoking and dual use. While exclusive CC smoking exhibits an inverse association likely driven by nicotine-mediated symptom masking, dual use presents a unique synergistic risk. This suggests that combined exposure to multiple tobacco products may exacerbate mucosal inflammation and barrier dysfunction, overriding any suppressive effects of nicotine.