Testing of cough reflex sensitivity in children suffering from allergic rhinitis and common cold

Cough associated with upper respiratory tract disorders is a common and troublesome problem in children and little is known about the etiology of this type of cough. This study examined the capsaicin cough sensitivity (CS) in children suffering from allergic rhinitis (AR) and upper respiratory tract infection (URI), comparing it with that in healthy children taken as controls (C). CS to capsaicin, spirometry, skin prick tests, and nose-throat examination were performed in 61 children grouped by the diagnosis of AR, URI, and C. The results, in order of C vs. AR vs. URI, expressed as a geometric mean (±95% CI) log10 µM of capsaicin for C2 (the lowest concentration of capsaicin in µmol/l required to induce 2 coughs) were: 1.8 (1.6-1.9) vs. 1.0 (0.8-1.2) vs. 0.48 (0.2-0.8), P<0.001 and for C5 (the lowest concentration of capsaicin in µmol/l required to induce 5 coughs) 2.9 (2.8-2.9) vs. 2.6 (2.5-2.6) vs. 2.1 (2.0 –2.3), P<0.05. We found that CS in children with AR, even when tested out of pollen season, was significantly heightened compared with controls. CS in children with URI was extremely high compared with both C and AR groups. We conclude that pathological processes in the nose of any etiology could cause a sensitization of the cough reflex with decreased cough threshold during asymptomatic period of AR. Cough also is enhanced by acute inflammation in the upper airways in nonatopic children.