McGarvey et al have described the causes of cough and the predictive values of appropriate diagnostic tests in a group of patients presenting to a specialist clinic.1 They have used a histamine challenge test to support the diagnosis of asthma and to justify a trial of inhaled corticosteroid therapy. We agree with the authors’ conclusion that a negative histamine challenge effectively rules out asthma as the cause of chronic cough, but disagree that this obviates the need for a trial of inhaled corticosteroids. Eosinophilic bronchitis presents with a chronic cough and sputum eosinophilia, but without the variable airflow obstruction or airway hyperresponsiveness seen in asthma.2In common with asthma and in contrast to patients with cough without sputum eosinophilia, the cough improves with inhaled corticosteroid therapy. Eosinophilic bronchitis can only be diagnosed if airway inflammation is assessed.

We have prospectively looked for evidence of eosinophilic bronchitis in new patients referred over a two year period with isolated chronic cough.3 …