A bout of stabbing pain in the right chest and armpit may be due to tissue muscle strain or strain injury, or it may be caused by intercostal neuritis, pleurisy, mastitis and other diseases. If you keep a bad posture for a long time, improper exercise or suffer from violent external impact, etc., it may lead to the right chest and armpit local tissue muscle strain, damage, manifested as local pain, change position or coughing when the pain can be aggravated. Patients with intercostal neuritis usually feel a stabbing pain in the chest and ribs along the nerve course. Most patients will be accompanied by symptoms such as loss of appetite and weakness in the limbs. Pleurisy, such as tuberculous pleurisy, with pleural involvement, manifests itself as chest pain and chest tightness, mostly accompanied by systemic symptoms such as low-grade fever and malaise. Lactating women may have red, swollen and hot pain in the breasts due to milk stagnation, and the pain may radiate to the armpits. Severe cases may be accompanied by fever and abscess formation. There are other causes of right chest and axillary pain, and it is recommended that patients seek timely medical treatment to avoid delaying the condition.