3. Waking at night due to asthma on two consecutive nights A severe exacerbation will be defined as any need for additional medical contact for treatment of asthma (e.g. Emergency Room, Walk-in Clinic) or any hospital admission for asthma. The need for oral corticosteroids will also constitute a severe exacerbation. If at any point the subjects undergo a severe exacerbation, they will be examined by either their own treating physician or by one of the physicians associated with this study and appropriate escalation of treatment will be commenced. The REB will be informed of all severe exacerbations. The study coordinator and one of the study physicians will be available by pager around the clock during the course of the study.