Inhaled environmental antigens, . allergens, cause allergic symptoms in millions of patients worldwide. As little is known about the fate of an aller-gen upon inhalation, we addressed this issue for a major dust mite allergen, Der p 2. First, a model for Der p 2-sensitization was established in C57BL⁄6 J mice, in which sensitized mice mounted a Der p 2-specific IgE-response with eosinophilic lung inflammation after allergen challenge in the airways.