Blushing is usually caused by a variety of reasons, such as heart disease, lung disease and abnormal liver function, which may cause patients to blush. 1. Heart diseases include congenital heart disease, coronary heart disease, heart valve disease, dilated cardiomyopathy and heart failure. Because the heart is an organ that needs blood and oxygen, an unhealthy heart will cause the whole body to be unable to supply oxygen, resulting in a decrease in the oxygen saturation of arterial blood, and the patient will turn blue. 2. Lung diseases, including severe infections, pulmonary embolism, chronic obstructive pulmonary disease, pulmonary hypertension, pulmonary heart disease, respiratory failure, interstitial fibrosis, pulmonary encephalopathy, lung cancer, etc., may cause a decrease in oxygen saturation, resulting in bluish color. 3. Others: such as abnormal liver function, poisoning, drowning, electric shock, shock caused by various reasons, etc., respiratory and circulatory disorders, may also cause bluish color. In short, the emergence of blue face should be timely medical examination, such as coronary CTA, cardiac ultrasound and chest CT and other examinations, targeted treatment.