Allergens, germs and asthma

OBJECTIVE: To explore asthma pathogenesis using data from upper and lower airways. DATA SOURCE: English-language papers on human asthma and nasal polyp subjects from 1990 onwards. STUDY SELECTION: High-quality studies in established journals. RESULTS: The recognition of its inflammatory nature led to a quantum leap in the understanding and treatment of asthma, with lives saved by inhaled corticosteroids. Further work at genetic, molecular, histological and clinical levels has shown that asthma is polymorphic and rarely involves isolated Th2 bronchial inflammation. Viral infections may act as an initiating event in children and adults, showing synergy with atopy. Chronic staphylococcal colonization of the mucosa may act as a promoter, as in atopic dermatitis. These two observations may be linked, with viruses providing an entry for bacteria into the mucosal epithelium. CONCLUSIONS: Most asthma begins in the nose and involves allergy and infection: both viral and bacterial. The combination of atopy and infection suggests new possibilities for therapy.