Quality of Life and Capsaicin Sensitivity in Patients with Airway Symptoms Induced by Chemicals and Scents: A Longitudinal Study

Abstract

ObjectiveIt is common in asthma and allergy clinics to see patients presenting with upper and lower airway symptoms that are induced by chemicals and scents and not explained by allergic or asthmatic reactions. Previous studies have shown that these patients often have increased cough sensitivity to inhaled capsaicin; such sensitivity is known to reflect the airway sensory reactivity. The aim of this study was to evaluate the duration of symptoms induced by chemicals and scents and to measure health-related quality of life (HRQL) in patients with chemically induced airway symptoms. We also wished to determine and compare repeatability of the cough response to capsaicin inhalation, and to evaluate the patients’ airway sensory reactivity in a long-term perspective.ParticipantsSeventeen patients with a history of at least 12 months of airway symptoms induced by chemicals and scents were followed over 5 years with repeated questionnaires, measurements of HRQL, and capsaicin inhalation tests.ResultsThe symptoms persisted and did not change significantly over time, and the patients had a reduced HRQL that did not change during the 5-year period. The capsaicin sensitivity was increased at the start of the study, the cough sensitivity was long-lasting, and the repeatability of the capsaicin inhalation test was considered to be good in a long-term perspective.ConclusionsUpper and lower airway symptoms induced by chemicals and scents represent an entity of chronic diseases, different from asthma or chronic obstructive pulmonary disease, with persistent symptoms, a reduced HRQL, and unchanged sensory hyperreactivity.

Inhaled ethanol potentiates the cough response to capsaicin in patients with airway sensory hyperreactivity

“…A preinhalation of 5% or 25% ethanol enhanced the cough reaction to capsaicin. A control group without airway symptoms did not have the corresponding reactions and coughed significantly less than the patients in accordance with earlier studies [3,5,24].…”

“…Before each test a pre-inhalation was given in a double-blind and randomized fashion, of either 1 mL saline, or 1 mL of 5% or 25% ethanol. The test was initiated with a pre-inhalation of either 1 mL saline, or 1 mL ethanol (5% or 25%) for 6 minutes, followed by 4 minutes of rest, as previously described [3,5]. Thereafter, the subject was provoked in the same manner with two concentrations of capsaicin, namely, first 0.4 and then 2.0 µmol/L, in a 1 mL solution.…”

“…The condition is therefore called "sensory hyperreactivity (SHR)", and it affects more than 6% of the adult population in Sweden [3]. Common symptoms are nasal blockage, rhinorrhea, eye irritation, heavy breathing, cough, hoarseness, and phlegm, as well as general symptoms, such as headache and nausea [4,5]. After capsaicin inhalation, changed levels of nerve growth factor in nasal secretions have been detected, indicating a neurochemical imbalance in the airways, which is related to SHR [6].…”

“…Patients with SHR react more strongly than healthy individuals to provocation with inhaled capsaicin, and the cutoff values for a positive reaction have been determined [4]. The capsaicin inhalation test in the diagnosis of SHR has good short-term and long-term reproducibility [5,9]. Capsaicin, the main, pungent ingredient in chili, stimulates the unmyelinated C-fibers of the sensory nervous system, giving a burning sensation by activating the ion channel of transient receptor potential vanilloid subunit 1 (TRPV1) [10].…”

Are there clinical features of a sensitized cough reflex?

“…A recent longitudinal follow up of SHR patients over 5 years using repeat quality of life questionnaires and cough reflex sensitivity testing has suggested this syndrome persists unchanged over time [29]. While the existing literature provides important information on the extent of the problem, the definition of SHR, as currently exists, fails to include the non-chemical noxious stimuli that are important aggravants of cough.…”