Final answer:
Intrinsic asthma is a type of asthma that does not involve an allergic reaction and its onset is usually in adolescence.
Step-by-step explanation:
A characteristic of intrinsic asthma is that the onset is usually in adolescence. Intrinsic asthma is also known as non-allergic or non-atopic asthma, and it is different from extrinsic asthma, which is also known as allergic or atopic asthma. While extrinsic asthma is IgE-mediated and often triggered by allergens, intrinsic asthma is not IgE-mediated and can be triggered by factors such as exercise, cold air, or respiratory infections. Attacks of intrinsic asthma can be severe, similar to extrinsic asthma attacks.