People between 18 and 50 years of age who have had allergic asthma for at least 1 year may participate in this study. Candidates' medical, allergy and medication histories will be reviewed, and they will have a physical examination, including routine blood tests, urinalysis, electrocardiogram (EKG), and lung function test. Blood will also be drawn to test T cell response to allergens, and 12 skin tests (similar to a tuberculosis skin test) will be done to test for sensitivity to various allergens.