Asthma is a complex disease that often starts early in life. Exacerbations can be triggered by a number of agents such as allergens, respiratory infections, environmental tobacco smoke and pollutants, drugs, chemicals, exercise, cold air, infections and strong emotion making asthma therapy difficult and sometimes complicated. Multiple medications are often required to treat symptoms (bronchodilator agents such as beta-2 adrenergic agonists, theophylline, and anticholinergics), as well the underlying disease process (anti-inflammatory agents such as inhaled and systemic corticosteroids, cromolyn sodium and nedocromil; and leukotriene modifiers).