For Asthma group:  Inclusion Criteria:  Age 18-55 years Doctor diagnosis of asthma Previous asthma exacerbation  Exclusion Criteria:  Smoking history over past 12 months Sinonasal disease, including current symptoms of allergic rhinitis Asthma exacerbation or an upper respiratory viral infection within the previous six weeks Current or concomitant use of oral steroids, monoclonal antibodies or nasal sprays Neutralising antibodies to rhinovirus (RV)-16 Clinically significant diseases other than asthma which, in the opinion of the investigator, may either put the patient at risk because of participation in the study, influence the results of the study, an/or the patient's ability to take part in it Inability to understand written or verbal information in English  For healthy control group:  Inclusion Criteria:  • Age 18-55 years  Exclusion Criteria:  As for Asthma group and in addition:  • History of asthma