Sputum and plasma levels of IL-17 are increased in stable asthmatics with obesity. Raised sputum IL-17 contributes to airway neutrophilia in obese stable asthmatics. Higher plasma IL-17 correlates positively with depressive symptoms in stable asthma. Obesity may not adversely influence the severity of an asthma exacerbation. IL-17 expression is increased and plays a role in acute asthma.