Soreness in the armpit may be caused by physiological reasons such as overwork, cold environmental stimulation; it may also be caused by pathological factors such as cervical spondylosis and breast diseases. 1. Physiological reasons: there are many muscles, tendons and other soft tissues attached to the armpits. Long-term shoulder activities such as physical exercise may lead to soft tissue damage under the armpits and aseptic inflammation, resulting in the accumulation of metabolic products such as lactic acid and pain. Prolonged stimulation by cold environment will cause localized vasoconstriction of the axilla, and the above symptoms may also occur. Generally, it can recover by itself and does not need treatment. 2. Pathological factors: cervical spondylosis may compress the nerve tissues that innervate the armpit area, causing sensory and motor abnormalities in the armpit area, which may also cause symptoms of underarm pain. 3. Breast diseases: Breast diseases such as breast cancer and mastitis may lead to enlargement of lymph nodes in the armpits, which may also lead to symptoms of underarm pain. There may be other reasons for underarm pain, so it is recommended that you go to the hospital in time, complete the examination to clarify the cause of the disease, and then give targeted treatment or therapy under the guidance of the doctor.