It is usually normal to have lymph nodes in the armpit. There may be some unknown causes in the body that stimulate the lymphatic system and result in swollen axillary lymph nodes. Swollen axillary lymph nodes are commonly caused by local inflammation, lymphoma and tumor metastasis, as follows: 1. Local inflammation: such as axillary abscesses and mastitis in lactating women may lead to swollen axillary lymph nodes. In this case, oral antibiotic anti-inflammatory treatment or axillary abscess incision and drainage is required, and the lymph nodes can return to normal after treatment. 2. Lymphoma: Tumors and blood disorders can lead to swollen lymph nodes in the supraclavicular fossa, axilla and subclavian fossa, but mostly without pain. At this time, care should be taken and even ultrasound and pathological examination is needed; 3. Tumor metastasis: tumor axillary lymph node metastasis may lead to axillary lymph node enlargement.