Protocol schema. Screening visit identifies subjects with mild asthma who are atopic. During first bronchoscopy, BAL is performed in lingula (baseline), diluent is applied in RUL, and allergen is applied in RML. After approximately 10 h, subject undergoes HRCT scan and 2 PET scans: 13NN-saline and 18F-FDG emission. Next morning, subject undergoes second bronchoscopy, during which BAL is performed in RUL and RML. BAL fluid is sent for cellular analysis from lingula and from RUL and RML.