Enlargement of submandibular lymph nodes may be caused by lymphadenitis, lymphoma, or diseases of neighboring organs. 1. Lymphadenitis: Infection of submandibular lymph nodes by external pathogenic bacteria will cause inflammatory reaction of lymph nodes, which will lead to swelling of submandibular lymph nodes. 2. Lymphoma: Lymphoma is a kind of malignant tumor, which can also cause the symptom of enlarged submandibular lymph nodes. 3. Diseases of neighboring organs: for example, infections around the teeth, infections in the throat, inflammation of the thyroid gland, otitis media and so on, can also cause swelling of submandibular lymph nodes. There may be other reasons for the swelling of submandibular lymph nodes, so you need to go to the hospital in time for examination and follow the doctor’s instructions for treatment.