Logistical challenges with research pharmacy prevented the dilution of the capsaicin. No participants were ever recruited, enrolled, or approached.

Irritable larynx syndrome (ILS) is a hyperkinetic laryngeal dysfunction that is characterized by a persistent cough, voice changes, or breathing difficulties, which are often triggered by an irritant. Diagnosis of ILS is difficult and typically made via a thorough review of the clinical history and, occasionally, the patient's reaction to an odor-provocation test. Standard treatment for ILS is behavioural therapy with a speech language pathologist (SLP), which provides symptom improvement for most patients. However, currently, there are no objective measures of the upper airway hyper-responsiveness in this condition to assist in diagnosing and monitoring disease severity.

Since the cough is irritant-based, it is anticipated that patients with ILS will have a hypersensitivity to the irritant capsaicin. Capsaicin is the active component of chili peppers and is what makes them hot. The capsaicin cough challenge is a well recognized test that involves inhaling different concentrations of capsaicin solutions to determine a cough reflex sensitivity.

The purpose of this research study is to confirm that ILS patients have a hypersensitivity to capsaicin compared to healthy volunteers. If a hypersensitivity is observed in ILS patients, the second objective of this study will be to see if behavioural therapy improves the cough reflex sensitivity in this patient population.

The proposed study has two purposes; the first is to utilize capsaicin cough challenge to demonstrate an increased efferent receptor sensitivity level in ILS subjects as compared to a control group. The second is to determine if there is an objective change in capsaicin cough challenge results after behavioral therapy, and whether it correlates to the subjective improvement. Self-reporting measures include two validated cough quality of life (QoL) questionnaires collected at the same intervals as the capsaicin testing.

ILS Participants:

Inclusion Criteria:

• Diagnosis of ILS as per the St Michael's voice clinic consultation
• Methacholine test performed
• Negative/borderline result for methacholine test and/or negative/incomplete response for asthma treatment
• Negative test result for gastroesophageal reflux or negative/incomplete response to reflux treatment
• Allergy test has been completed with negative result or does not account for all symptoms
• Agreed to behavioural therapy in SMH Voice Disorders Clinic

Exclusion Criteria:

• Active smoker
• Active respiratory disease (e.g., COPD, pulmonary fibrosis, lung malignancy.)
• Taking an ACE inhibitor
• Pregnant and/or breastfeeding
• Impaired liver and/or renal function
• Neurological disorder
• Psychiatric condition (outside of depression or anxiety)

Healthy Volunteers:

Exclusion Criteria:

• Active smoker
• Active respiratory disease (e.g. COPD, asthma)
• ILS diagnosis
• Chronic cough diagnosis
• Known hypersensitivity to capsaicin

ILS Patients