The causes of black and purple lips are as follows: 1. If the patient has black and purple lips, the first factor to be considered is poisoning. For example, acute nitrite poisoning, the patient will have intracellular hypoxia, intracellular asphyxia, so there will be lips, purple, cyanosis, etc. 2, cardiogenic diseases, such as coronary heart disease, myocarditis, pericarditis, rheumatic heart disease, heart valve disease, hypertensive heart disease. All of them will lead to coronary artery ischemia, lack of oxygen caused by insufficient blood supply and oxygen supply to cardiomyocytes, which will also lead to black and purple lips. 3, chronic respiratory diseases, such as chronic bronchitis, chronic bronchial dilatation, chronic obstructive pulmonary emphysema, chronic pulmonary heart disease, pulmonary hypertension will occur under the arterial blood oxygen saturation, oxygen partial pressure reduction, carbon dioxide partial pressure is too high, there will also be red and purple lips.