Which allergic-disease treatment is most effective but has the longest time to achieve clinical response?

• A. Antihistamines
• B. Immunotherapy
• C. Glucocorticoids
• D. Sympathomimetics

Answer: (B)

Allergen immunotherapy gradually retrains the immune system to tolerate the triggering allergens, leading to true change in the disease course. It is the most effective option for long-term symptom control and can reduce or modify progression of allergic disease, with benefits that can persist after stopping treatment. But the trade-off is a slow onset: meaningful improvement typically requires months of regular therapy, and full benefit often takes several years. In contrast, quick-acting antihistamines relieve symptoms within hours but don’t alter the disease process. Glucocorticoids are highly effective anti-inflammatories and work relatively quickly, yet they don’t modify the underlying tendency to react to allergens. Sympathomimetics provide rapid relief of nasal congestion but aren’t disease-modifying and carry risks with overuse.