This study will test the hypothesis that neurogenic dysfunction is a key mechanism underlying asthma, particularly in asthmatics who have no airway inflammation and for whom current asthma treatment is not effective (30-50% of all asthmatics). Induced sputum will be collected in 120 asthmatic and 60 non-asthmatic children and analysed for immune and neurogenic markers. Airway nerve control and sensitivity will be determined using physiological and challenge tests. We will assess whether asthma symptoms occur due to neurogenic mechanisms in the absence of airway inflammation. Interactions between neural mechanisms, inflammation and markers of airway structure will also be examined. Based on this, novel asthma phenotypes will be identified and their associations with stress and environmental exposures will be determined. The findings of this study are likely to lead to a paradigm shift in concepts of asthma aetiology and to identify novel pathways for effective interventions for all asthmatics.