The purpose of this study is to assess the effect of L-menthol on breathlessness and exercise capacity in patients with Asthma.

Dyspnea is a cardinal symptom in patients with lung disease, 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 COPD and 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 patients with Asthma.

Inclusion Criteria:

• the subject has given written consent to participate in the study
• physician diagnosis of Asthma according to international guidelines
• mMRC (modified Medical Research Council) score of 1 or above
• 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.