Hidden pain in the left armpit at the ribs may be an adverse symptom caused by intercostal neuritis, or discomfort caused by coronary heart disease, shingles and other diseases. 1. Intercostal neuritis: Intercostal neuritis may cause vague pain in the left armpit at the ribs, usually accompanied by a burning sensation, pins and needles and other symptoms, a large amount of upper limb activity or coughing when the pain will be aggravated, there will be pressure and pain, and the affected area of the muscle may appear stiff. 2. Coronary heart disease: coronary heart disease may also cause the left armpit ribs hidden pain, patients usually appear obvious chest tightness and shortness of breath, chest pain and other adverse symptoms, accompanied by panic, angina and other discomforts, the condition of the onset of sudden dizziness or shock. 3. Herpes zoster: vague pain in the left armpit at the ribs may also be suffering from the discomfort caused by herpes zoster, is due to herpes virus infection caused by the disease, the affected area may appear swelling, pain, numbness and other undesirable symptoms, some patients may have fever. Such discomfort symptoms, but also consider other reasons, a short period of time can not be relieved, you need to seek medical attention to avoid further development of the disease.