Inflammatory and oxidative stress biomarkers in allergic rhinitis: the effect of smoking

Background Accumulating evidence confirms the presence of pan‐airway inflammation in allergic rhinitis patients. Smoking is known to affect the asthmatic airway inflammation. However, no study has evaluated the impact of smoking on airway inflammation of allergic rhinitis patients. Objective The aim of the present study was to evaluate the impact of smoking on inflammatory and oxidative stress biomarkers in patients with seasonal allergic rhinitis, using non‐invasive methods for sample collection. Methods Forty patients with seasonal allergic rhinitis (20 smokers and 20 non‐smokers) and 30 healthy subjects (15 smokers and 15 non‐smokers) were recruited for the study during pollen season. All subjects were submitted to measurement of the fraction of exhaled NO (FeNO), exhaled breath condensate (EBC) collection, nasal lavage collection, pre‐ and post‐ bronchodilation spirometry and metacholine bronchial challenge testing. pH, leukotriene B₄ (LTB₄) and 8‐isoprostane were determined in EBC and nasal lavage samples. Results Patients with allergic rhinitis presented higher LTB₄ and 8‐isoprostane levels in nasal lavage (P<0.0001 for both comparisons), with no significant differences between smokers and non‐smokers. Patients with allergic rhinitis also presented higher LTB₄ levels and lower pH in EBC (P<0.001 and P=0.004, respectively), with prominent differences between smokers and non‐smokers (P<0.0001 and P=0.003, for LTB₄ and pH, respectively). A significant correlation between nasal lavage and EBC LTB₄ values was observed (r_s=0.313, P=0.048). Conclusions Patients with allergic rhinitis present increased LTB₄ and 8‐isoprostane in their nasal cavity, however, with no significant differences between smokers and non‐smokers. In contrast, smokers with allergic rhinitis present higher LTB₄ levels and lower pH in EBC, suggesting that these patients may be more susceptible to the deleterious effects of smoking, compared with non‐smokers.