Black and purple lips may be caused by environmental factors, poisoning, heart and lung diseases. 1. Environmental factors: If you are in a cold environment for a long time, the blood circulation will be slow, and the blood in the mouth localization stays for too long, or located in the plateau, the oxygen content is low causing hypoxia, resulting in black and purple lips. 2. Poisoning: for example, acute nitrite poisoning, the patient will appear intracellular oxygen deficiency, intracellular asphyxia, so there will be black and purple lips and so on. 3. Heart or lung disease: cardiopulmonary disease can lead to lack of oxygen in the blood circulation, which is manifested by cyanosis at the end of the circulation and the appearance of black and purple lips. There may be other reasons for the appearance of black and purple lips, it is recommended to go to the hospital in time, improve the examination to clarify the cause of the disease, and then give targeted treatment or treatment.