Effect of Sex Hormone During the Menstrual Cycle on Capsaicin Evoked Cough Responses

Inclusion Criteria: 1. Subjects must be aged between 18 to 35 years 2. Have a diagnosis of atopic asthma (based on at least one positive skin prick test and methacholine PC20 ≤16 mg/ml) 3. FEV1 ≥ 70% of predicted 4. Demonstrate a cough response to capsaicin with a minimum of 3 coughs during the screening capsaicin challenge Exclusion Criteria: 1. Subjects who are in a pollen season that affects their asthma 2. Subjects who report allergies to capsaicin or bronchoconstrict at the end of the full dose capsaicin cough challenge and require short acting bronchodilator therapy (assess after visit 1) 3. Subjects who do not display evidence of airway hyper-responsiveness (methacholine PC20\>16mg/ml) (assess after visit 1) 4. Symptoms of upper respiratory tract infection in the last 1 month which have not resolved. 5. Lower respiratory tract infection or pneumonia in the last 6 weeks. 6. Current smoker or ex-smoker with ≥10 pack year smoking history and abstinence of ≤6 months 7. Asthma exacerbation in the previous month requiring a start of inhaled or oral corticosteroids. 8. Any asthma medication with the exception of infrequent (less than twice weekly) short-acting β2-agonist. 9. Subjects who have changed asthma medication within the past 4 weeks prior to screening 10. A previous asthma exacerbation requiring Intensive Care Unit admission. 11. Significant other primary pulmonary disorders in particularly; pulmonary embolism, pulmonary hypertension, interstitial lung disease, lung cancer, cystic fibrosis, emphysema or bronchiectasis. 12. Pregnancy or breast-feeding 13. Use of ACE inhibitors 14. Any centrally acting medication (opioids, gapapentin, pregabalin, amitriptyline) which in the view of the investigator could alter the sensitivity of the cough reflex 15. History of psychiatric illness, drug or alcohol abuse which may interfere in the participation of the trial. 16. History of current or previous anabolic steroid use in men. 17. For the natural cycle group, the female patients must have regular (24 to 35 day) natural cycles and no oral contraceptive use for ≥6 months 18. For female's taking the oral contraceptive pill they must be taking this ≥6 months 19. Use of B-blockers 20. Patients with clinically significant cardiovascular disease 21. Patients with known allergy to any of the study medications or excipients 22. Patients with a known potentially life threatening allergy (e.g. food allergy, stinging insect allergy), history of anaphylaxis, mastocytosis, angioedema