Must not use theophylline, oral or inhaled corticosteroids, nedocromil sodium, cromolyn sodium, zilueton, leukotriene receptor antagonists (e.g., zafirlukast or montelukast), or anti-cholinergic agents within the prior 3 months. In addition, patients requiring ongoing therapy with anti-histamines, hydroxyzine, and tricyclic anti-depressants will be excluded. Research subjects can continue therapy with inhaled beta-agonists during the study.