A lymph node under the left parotid sometimes big and sometimes small may be caused by lymphadenitis, lymph node tuberculosis, lymph node tumor and other diseases. 1. Lymphadenitis: mainly due to pathogen infection in the oral cavity, nasopharynx, etc., autoimmune deficiency, trauma factors lead to inflammatory lesions in the lymph nodes of the left cheek. Inflammatory mediators stimulate the lymph nodes, causing lymphadenitis, and the lymph nodes may appear large or small when the condition changes. 2. Lymph node tuberculosis: usually caused by Mycobacterium tuberculosis infection. In the clinic, the patient’s lymph nodes will be enlarged, and with the change of the condition, the lymph nodes may appear to be big or small at times. 3. Lymph node tumors: usually malignant tumors metastasize through lymphatic transfer, resulting in tumor lesions in lymph nodes. If the treatment of radiotherapy and chemotherapy is incomplete, the patient may have lymph nodes that are sometimes large and sometimes small. Patients with abnormal lymph nodes should go to the hospital for examination in time, and then choose the appropriate method for treatment after finding out the specific cause under the guidance of the doctor.