Effects of intranasal histamine on the cough reflex in subjects with allergic rhinitis.

In the present study we investigated the effects of nasal histamine on the intensity of coughing and the effects of intensified nasal breathing following nasal histamine on cough sensitivity (CS) in 14 subjects with seasonal allergic rhinitis. The study consisted of two parts performed one week apart. First, baseline CS to capsaicin was determined, followed by intranasal histamine challenge (4 mg/ml, 0.1 ml) and the count of the number of coughs to inhaled capsaicin on the background of most intensive nasal symptoms (sneezing, itching, rhinorrhea, and nasal blockage) evoked by histamine. In the second part, CS was determined after intranasal histamine followed by 10 min of intensified nasal breathing through the nose or mouth in a randomized order at 2-day intervals. The number of coughs induced after intranasal histamine was significantly higher, compared with intranasal saline, [9 (7-12) vs. 4.5 (4-6), P<0.001]. CS also was significantly increased after nasal histamine, but nasal intensified breathing failed to cause any changes in CS. We conclude that stimulation of nasal mucosa with histamine enhanced the cough response in subjects with allergic rhinitis.