Objective To explore the effect of lower airway inflammation on the pathogenesis of upper airway cough syndrome( UACS) . Methods Ten cases of UACS and 10 cases of chronic rhinitis or sinusitis without cough were enrolled as group A and group B, respectively. And 10 healthy volunteers were included as controls( group C) . The cough threshold C2 and C5 to inhaled capsaicin, defined as the lowest concentration of capsaicin required to induce ≥2 and ≥5 coughs, was measured. The total and differential cell counts was determined in induced sputum, and the levels of histamine and prostaglandin E2 were analyzed in supernatant of sputum. Results Cough threshold was significantly lower in group A than group B [ C2: ( 0.65 ±0. 08) μmol / L vs ( 3.90 ±1. 37) μmol / L; C5: ( 1.59 ±0. 28) μmol / L vs ( 33.46 ±23. 71) μmol / L, P lt;0. 05] and comparable between group B and group C( P gt; 0. 05) . Group A, similar to group B( P gt; 0. 05 ) , contained more inflammatory cells, with decreased percentage of macrophages and increased percentage of neutrophils in induced sputum than group C( P lt; 0. 05) . Furthermore, the levels of histamine[ ( 9. 55 ±1. 89) ng/mL vs ( 2. 37 ±0. 25) ng/mL, P lt; 0. 05] and prostaglandin E2 [ ( 361. 71 ±39. 38) pg/mL vs ( 144. 34 ±15. 69) pg/mL, P lt; 0. 05] were higher in supernatant of induced sputum from group A than group B, while the latter was not different from group C( P gt; 0. 05) . Conclusion Increased cough sensitivity caused by airway inflammation may be important for the pathogenesis of UACS, and the activation of mast cells in mucosa of lower airway might be an important factor.