The causes of swollen submandibular lymph nodes include the following: First, it is considered to be caused by inflammation of the oral system, including acute and chronic gingivitis, acute suppurative tonsillitis, chronic tonsillitis, acute pharyngitis, and chronic pharyngitis, which can stimulate swollen submandibular lymph nodes. Secondly, it is considered to be caused by thyroid diseases, including thyroid tumor, subacute thyroiditis, and Hashimoto’s thyroiditis, which can cause swollen submandibular lymph nodes. In the third aspect, the causes of swollen lymph nodes also include systemic system diseases, including immune system diseases and lymphoma, which can also cause swollen submandibular lymph nodes. There are many causes of swollen submandibular lymph nodes, and most of them are reactive hyperplasia caused by inflammation, which will subside by taking antibacterial and anti-inflammatory drugs and eating a light diet. If it does not subside repeatedly for a long time, ultrasound examination is needed to clarify.