Which of the following conditions would most likely require corticosteroid therapy?

Corticosteroid therapy is particularly beneficial in situations characterized by significant airway inflammation. This is because corticosteroids have potent anti-inflammatory effects, which can help reduce swelling, mucus production, and overall airway hyperreactivity. Conditions with substantial airway inflammation—such as asthma exacerbations, chronic obstructive pulmonary disease (COPD) flare-ups, and other inflammatory respiratory conditions—often require corticosteroid treatment to control the inflammatory process and improve lung function.

The other conditions listed may involve airway issues but do not primarily necessitate corticosteroid therapy. For instance, acute bronchospasm is typically treated with bronchodilators to provide immediate relief rather than anti-inflammatory drugs. Chronic lung diseases may be managed with a variety of treatments where corticosteroids might be used in specific situations but are not always the first line. Allergic reactions might sometimes be treated with corticosteroids, but this is usually in the context of significant symptoms rather than being a routine requirement. Therefore, significant airway inflammation is the most direct and appropriate indication for corticosteroid therapy.