**Core Concept**
Thornwaldt's abscess is a rare, chronic condition involving the formation of a cystic mass in the midline of the posterior wall of the nasopharynx, often associated with a congenital anomaly of the pharyngeal bursa. The abscess results from the accumulation of lymphoid tissue and fluid within the bursa.

**Why the Correct Answer is Right**
Antihistaminics are not a primary treatment for Thornwaldt's abscess, as the condition is not primarily an allergic reaction. The mainstay of treatment involves addressing the abscess directly, either through marsupialization or removal of the lining, to prevent recurrence. Antibiotics may be used to manage secondary infections, but antihistamines are not a relevant treatment. The pharyngeal bursa's lymphoid tissue is not typically associated with allergic reactions, making antihistamines an ineffective treatment option.

**Why Each Wrong Option is Incorrect**
**Option A:** Antibiotics may be used to manage secondary infections associated with Thornwaldt's abscess, but they are not a primary treatment for the condition itself.
**Option B:** Marsupialization is a recognized treatment for Thornwaldt's abscess, involving the creation of a new epithelialized tract to facilitate drainage of the abscess.
**Option C:** Removal of the lining is another treatment approach for Thornwaldt's abscess, often performed to prevent recurrence.

**Clinical Pearl / High-Yield Fact**
A key consideration in managing Thornwaldt's abscess is the potential for complications, including chronic rhinitis, nasal obstruction, and recurrent infections. Successful treatment requires a multidisciplinary approach, involving otolaryngology, infectious disease, and possibly other specialties.

**✓ Correct Answer: D. Antihistaminics**