What is shortness of breath? Shortness of breath is a common symptom of allergy, infection, inflammation, injury, or certain metabolic conditions. The medical term for shortness of breath is dyspnea. Shortness of breath results when a signal from the brain causes the lungs to increase breathing frequency. You may also experience shortness of breath because of conditions affecting the lungs or entire pulmonary system, or in association with more generalized conditions, such as obesity or low blood pressure (hypotension). Inflammation of the lungs and bronchial tubes are also common causes of shortness of breath, as is injury to the respiratory tract caused by smoking or other toxins. Shortness of breath may occur with injury to the lungs, such as a collapsed lung (pneumothorax). Numerous heart conditions that lead to low oxygen levels in the blood (hypoxia) also result in shortness of breath. Depending on the cause, you may experience shortness of breath only while lying down or when either lying down or sitting up. Shortness of breath can be accompanied by sputum production, sneezing, wheezing, or rapid heart rate (tachycardia). Allergic asthma reactions lead to shortness of breath, which can be severe and even life threatening. Most, if not all, lung diseases involve shortness of breath and, in rare cases, shortness of breath may present as a symptom of serious infections of the lungs or bronchial tubes, such as pneumonia or bronchiolitis in young children. Congestive cardiac failure, a heart condition, may be accompanied by shortness of breath in addition to other symptoms, including pink, frothy mucus, rapid breathing (tachypnea), wheezing, and rapid heartbeat. Shortness of breath can also be an indication of lung cancer, especially if accompanied by hemoptysis (coughing up blood). Seek immediate medical care (call 911) if you have shortness of breath accompanied by any life-threatening symptoms, including bluish coloration of lips, fingernails or skin, confusion or loss of consciousness for even a brief moment, high fever (higher than 101 degrees Fahrenheit), sudden swelling of the face, tongue or lips, chest pain or pressure, or rapid heart rate (tachycardia). If your shortness of breath persists, worsens, or causes you concern, seek prompt medical care.