There are many reasons for pain under the armpit when pressed, and the cause should be identified and treated symptomatically. First, the pain under the armpit when pressed is in many cases caused by swollen lymph nodes, which may be caused by inflammation on the one hand, or by lymphatic metastases from some malignant diseases on the other. If the swollen lymph nodes are caused by inflammation, the blood test will reveal elevated white blood cells, and there may be local skin inflammation or inflammation such as upper respiratory tract infection. If it is caused by a malignant tumor, the original cause should be found and then treated symptomatically. Second, the pain under the armpit may be caused by some local infections, such as skin canker sores or local pain caused by inflammation of sebaceous cysts, etc. This condition is not difficult to find through local examination, and treatment is based on the use of anti-inflammatory drugs and local ointment treatment. Third, the pain under the armpit may also be caused by muscle strain, which has a clear history of trauma and can be cured by rest and the use of some blood-stasis-boosting drugs.