**Question:** Most common allergic manifestation of tuberculosis is :

A. Contact dermatitis
B. Drug reaction
C. Acute exudative pleurisy
D. Chronic exudative pleurisy

**Core Concept:** Tuberculosis is an infectious disease caused by the bacterium Mycobacterium tuberculosis. Allergic reactions to tuberculosis are uncommon but can occur due to the host's immune response to the bacteria. The most common presentations involve skin reactions, pleural involvement, or drug reactions.

**Why the Correct Answer is Right:** The correct answer, **D.** Chronic exudative pleurisy, refers to an allergic response to tuberculosis, where the immune system mounts an excessive inflammatory response against the bacteria. Chronic exudative pleurisy results in accumulation of fluid between the pleural layers, causing signs and symptoms associated with pleural effusion.

**Why Each Wrong Option is Incorrect:**

A. **Contact dermatitis:** This refers to a localized skin reaction due to direct exposure to the causative agent, such as via skin contact. It is not the most common allergic manifestation of tuberculosis, as it is primarily a respiratory infection.

B. **Drug reaction:** Although tuberculosis treatment may cause drug reactions, this option does not specifically address an allergic manifestation of tuberculosis itself.

C. **Acute exudative pleurisy:** This represents a rapid accumulation of fluid between pleural layers due to inflammation and is not specific to an allergic response in tuberculosis infection.

**Clinical Pearl:** Tuberculosis can manifest variously, and the correct answer, chronic exudative pleurisy, highlights a specific allergic response to the infection. It is essential for medical students and practitioners to be familiar with these diverse clinical presentations to diagnose and appropriately manage tuberculosis cases.