Swelling of axillary lymph nodes may be caused by inflammation and infection or tumor, systemic lupus erythematosus and so on. 1. Inflammation: If you don’t pay attention to the cleanliness and hygiene of armpit for a long time, the soft tissues around the armpit will be infected with inflammation, which will induce folliculitis, and the repeated stimulation of inflammation will cause swollen lymph nodes in the armpit. Common inflammatory infections include folliculitis, mastitis and pneumonia. 2. Tumor: some malignant tumors with lymph node metastasis may also cause axillary lymph node enlargement, such as lung cancer, breast cancer, etc. With the aggravation of the disease, it may also cause upper limb activity disorder. 3. Connective tissue diseases: such as systemic lupus erythematosus, tuberculosis and other lesions, which will lead to the enlargement of lymph nodes in some places of the body, including axillary lymph nodes. It is recommended to go to the hospital for examination to clarify the cause of the disease before treatment.