The most common cause of left submandibular lymph node enlargement is infection. Oral infection or gingivitis can easily lead to regional lymph node enlargement, and the patient will also have significant pain and even fever. In the acute stage, anti-infection treatment is needed. In the usual daily life, one should also pay attention to oral hygiene and insist on rinsing the mouth with warm salt water, which can significantly relieve the patient’s discomfort and reduce the chance of infection, as well as avoiding stimulating foods and excessively spicy foods. Some patients with tumors or viral infections may also have swollen local lymph nodes, marked loss of appetite, weight loss, and anemia in laboratory tests. Patients with early diagnosis may opt for surgical treatment or adjuvant radiotherapy.