Sensitivity to methacholine and capsaicin in patients with unclear respiratory symptoms.
BACKGROUND
Capsaicin, the pungent ingredient in red pepper, is known to stimulate coughing via the sensory nervous system. Earlier studies showed that patients with airway symptoms induced by chemicals and strong scents cough more after inhalation of capsaicin than healthy control subjects and this has been interpreted as a hyperreactivity of airway sensory nerves. Our aim was to study airway sensitivity to inhaled capsaicin and the occurrence of airway symptoms induced by strong scents in patients who underwent a bronchial methacholine test, primarily because of suspected asthma.


METHODS
Fifty-two consecutive patients referred for testing with methacholine were also provoked with inhaled capsaicin in increasing concentrations. Cough sensitivity to capsaicin was compared with that in 40 healthy control subjects.


RESULTS
The patients coughed significantly more compared with the healthy control subjects with each dose of capsaicin (P < 0.0001). Twelve patients (23%) had a positive methacholine test, and of these, nine were diagnosed with asthma. There was no difference in capsaicin sensitivity between patients sensitive or insensitive to methacholine.


CONCLUSIONS
The majority of the patients had no increased sensitivity to methacholine but did demonstrate sensory hyperreactivity (SHR). SHR appears to be a common diagnosis in investigations of patients with obscure airway symptoms.
Ternesten-Hasséus
E
E
Asthma and Allergy Research Group, Department of Respiratory Medicine and Allergy, Sahlgrenska University Hospital, Gothenburg, Sweden.
Farbrot
A
A
Löwhagen
O
O
Millqvist
Eva
E
D000293:Adolescent; D000328:Adult; D001985:Bronchial Provocation Tests; D016085:Bronchoconstrictor Agents / Q000009:adverse effects*; D002211:Capsaicin / Q000009:adverse effects*; D003371:Cough / Q000139:chemically induced / Q000503:physiopathology; D004305:Dose-Response Relationship, Drug; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D008297:Male; D016210:Methacholine Chloride / Q000009:adverse effects*; D008875:Middle Aged; D011237:Predictive Value of Tests; D012130:Respiratory Hypersensitivity / Q000139:chemically induced* / Q000175:diagnosis / Q000503:physiopathology; D012882:Skin Tests; D011795:Surveys and Questionnaires; D013997:Time Factors; D014938:Work Capacity Evaluation
D016085:Bronchoconstrictor Agents; D016210:Methacholine Chloride; D002211:Capsaicin