Cough sensitivity in allergic rhinitis

The objective of this study was to evaluate capsaicin cough sensitivity in pollen sensitive patients with allergic rhinitis at the time of grass pollen season and out of it. Cough reflex sensitivity was defined as the lowest capsaicin concentration that evoked 2 or more coughs (C2). Capsaicin aerosol in doubled concentrations (from 0.02 to 200 micromol) was inhaled by a single breath. Two groups of pollen sensitive rhinitis subjects and a group of healthy controls were studied. The C2 for the 23 pollen sensitive patients of the first group, studied out of pollen season (January-February), was 0.22 micromol/l (0.06-0.76) (geometric mean + 95% CI), which was substantially lower than the 4.29 micromol/l (2.54-7.26) in 24 healthy volunteers (P=0.0001). In another group of 15 pollen sensitive patients, C2 was 0.84 micromol/l (0.14-5.20) out of pollen season and 0.11 micromol/l (0.03-0.33) during the pollen season (May-June) (P=0.04). We conclude that pollen-sensitive subjects who suffer of seasonal allergic rhinitis have significantly greater capsaicin cough sensitivity, regardless of them being in or out of pollen season. Subclinical inflammatory changes in the lower airways are probably responsible for this effect.