ABSTRACT
Asthma is a chronic disease of the airways characterized by reversible airflow obstruction, airway hyperresponsiveness (AHR) and persistent airway inflammation. Most patients with asthma can trace the origin of their disease to early childhood. While the etiological factors responsible for the onset of asthma remain largely unknown, considerable progress has been made towards identifying potential mechanisms involved in the maintenance or exacerbation of the disease. A variety of environmental factors can influence the activity of the disease in susceptible individuals. Among these factors, allergens and respiratory viruses are the best-known triggers of asthma exacerbations both in children and in adults.
