The presence of mucosal inflammation in the lower airways of atopic asthmatics and to a milder degree of atopic nonasthmatics suffering from rhinitis points to atopy and allergen exposure as risk factors for lower airways disease. The study of mechanisms which regulate the degree of inflammation should enable the understanding of why some individuals suffer from rhinitis alone whereas others go on to develop bronchial disease. This information should enable the development of prophylactic strategies to prevent atopy from expressing itself in the lower airways.