Extrinsic (atopic) asthma — which statement is true?

• A. It is non-allergic
• B. It is triggered only by exercise
• C. It is allergic with elevated IgE
• D. It has no relation to allergens

Answer: (C)

Extrinsic asthma is the allergic form of asthma driven by IgE-mediated sensitivity to environmental allergens. In this type, the immune system responds to substances like dust mites, pollen, animal dander, or mold by producing IgE antibodies. These IgE antibodies bind to receptors on mast cells and basophils; when the allergen is encountered again, it cross-links the IgE on these cells and triggers release of mediators such as histamine and leukotrienes. This cascade leads to bronchoconstriction and airway inflammation, producing the classic asthma symptoms. Because IgE is involved and the reaction is to specific allergens, elevated IgE levels are common, which is why this statement is true. This form is not non-allergic, not limited to exercise, and it is related to allergens.