The allergy-asthma connection.

Asthma and allergic rhinitis are both common conditions and, therefore, often present in the same patients. Also, among the various triggers for asthma, allergy is an extremely common provoking factor for both adult and pediatric patients. The nose and lungs are connected by neural reflexes, and nasal allergen provocation can cause bronchoconstriction, and bronchial challenge can result in nasal inflammation. Treatment of allergic rhinitis with nasal steroids improves asthma control of symptoms, decreases bronchial hyperreactivity, and improves forced expiratory volume in 1 second. Treatment of subjects who have both allergic rhinitis and asthma with antihistamines (both alone and in combination with decongestants) and/or leukotriene receptor antagonists results in improvements in both conditions.