Submandibular sialadenitis: This is an inflammation of the submandibular gland, often caused by bacterial infection, which can lead to swelling in the submandibular area. It's a common condition that matches the symptom description closely.

Dental infection or abscess: Infections originating from the teeth can spread to the surrounding tissues, including the submandibular space, causing swelling.
Submandibular lymphadenopathy: Enlargement of the lymph nodes in the submandibular area can be due to various causes, including infections, autoimmune diseases, or malignancies.
Submandibular gland stones (sialolithiasis): Stones in the submandibular gland or its ducts can cause obstruction, leading to swelling and pain.
Benign tumors of the submandibular gland: Tumors such as pleomorphic adenoma can cause swelling in the submandibular area.

Ludwig's angina: A severe infection of the submandibular space that can cause significant swelling, pain, and potentially life-threatening airway obstruction if not promptly treated.
Submandibular space abscess: An abscess in this area can lead to severe complications, including airway compromise and sepsis, if not adequately drained and treated.
Malignancy of the submandibular gland or lymph nodes: Although less common, cancer can present as a swelling in the submandibular area and is critical to diagnose early for effective treatment.

Ranula: A type of mucocele that occurs in the floor of the mouth, which can sometimes cause swelling that might be perceived as submandibular.
Branchial cleft cysts: Congenital anomalies that can present as swellings in the neck, including the submandibular area.
Submandibular gland cysts: Less common than other salivary gland cysts, these can cause swelling in the submandibular area.
Sjögren's syndrome: An autoimmune disorder that can affect the salivary glands, including the submandibular gland, leading to swelling among other symptoms.