Acute lymphadenitis: This is often the most common cause of acute cervical swelling, typically resulting from a bacterial or viral infection. The swelling is usually accompanied by pain, redness, and warmth over the affected lymph node.

Cellulitis or abscess: Bacterial infections of the skin and soft tissues can cause swelling, redness, and pain in the cervical area.
Thyroiditis: Inflammation of the thyroid gland can cause swelling in the anterior part of the neck.
Branchial cleft cyst: A congenital anomaly that can become infected and present as an acute swelling in the neck.
Dental infection: Infections from the teeth or gums can spread to the lymph nodes in the neck, causing swelling.

Malignancy (e.g., lymphoma, metastatic cancer): Although less common, malignancies can present with acute or subacute cervical swelling and must be considered to avoid delayed diagnosis.
Tuberculosis: Can cause cervical lymphadenopathy and is crucial to diagnose due to its public health implications and the need for specific treatment.
Lemierre's syndrome: A rare but serious condition involving thrombophlebitis of the internal jugular vein, typically following a bacterial pharyngitis, which can present with neck swelling and pain.

Carotid body tumor: A rare, usually benign tumor located at the bifurcation of the carotid artery, which can cause a painless neck mass.
Cervical thymic cyst: A rare congenital anomaly that can present as a neck mass.
Kikuchi disease: A rare form of lymphadenitis, more common in young women, which can cause cervical lymphadenopathy.
Castleman disease: A rare disorder that involves an overgrowth of cells in the lymphatic system, which can cause lymphadenopathy, including in the cervical region.