The study objective is to investigate in a placebo-controlled, double-blind manner the effect of inhaled corticosteroid (ciclesonide) on airway hyperresponsiveness measured as having PD15 mannitol. Treatment medication will be administered as follows: 320 microgram ciclesonide or placebo will be inhaled once daily. The study duration consists of a treatment period of 4 weeks. The study will provide further data on safety of ciclesonide.