The main reasons for the redness, swelling and pain of armpit lumps include the following: 1. It may be the swelling and pain caused by secondary infection of folliculitis and sebaceous cysts on the skin surface of the armpit, which is more common in clinical practice; 2. The redness, swelling and pain of armpit lumps may also be caused by the inflammation of lymph nodes in the armpit due to the bacterial infection of lymph nodes, which will lead to the swelling of armpit. Swelling, sometimes serious lymph nodes will turn into pus, or even broken, this kind of pain is more intense; 3, the redness, swelling and pain of armpit lumps may also be caused by lymphatic tuberculosis in the armpit, and there may be tumors, including lymphoma, metastatic lymph nodes, etc., which can cause these symptoms. In short, if you have pain in the armpit, you should go to the hospital in time, improve the relevant examination, find the exact cause of the disease, and then take the corresponding treatment.