The purpose of this study is to assess the effect of L-menthol on breathlessness and exercise capacity in patients with Interstitial lung disease (ILD).

Dyspnea is a cardinal symptom in patients with interstitial lung disease (ILD), often triggered by daily-life physical activities. To date, an effective pharmacologic treatment to relieve chronic dyspnea is lacking. Recent pilot data support that inhaled L-menthol can markedly decrease laboratory-induced dyspnea in ILD patients, likely through increased afferent feedback of airflow in the airways by inducing a cooling sensation through olfactory stimulation. The aim of this study is therefore to assess the effectiveness and mechanisms of inhaled menthol for relief of chronic dyspnea in patients with ILD.

Inclusion Criteria:

• The subject has given written consent to participate in the study
• Physician diagnosis of fibrosing ILD according to international guidelines
• age 18 years or older
• able to cycle
• able to understand and talk Swedish to participate in the study procedures, as judged by the Investigators.

Exclusion Criteria:

• Resting peripheral oxygen saturation (SpO2) < 92%
• hospitalization or clinical instability during the last four weeks
• treatment with supplementary oxygen at rest or during exercise
• contraindication to exercise testing in accordance with clinical practice guidelines
• expected survival shorter than six months as judged by the Investigator
• medical conditions including congestive heart failure, acute coronary artery disease, neuromuscular diseases, severe psychiatric illness, and olfaction disorder.