The lips are generally caused by lack of oxygen or bad habits. For example, long-term heavy smoking, drinking, tobacco, toxic substances into the body, will lead to hemoglobin oxygen-carrying capacity decreased, and the lips dark. Long-term alcohol consumption will lead to increased blood viscosity, blood circulation is sluggish, causing the body lack of oxygen and lead to the lips. The dark lips are also seen in various diseases, such as emphysema, pulmonary stasis, pulmonary edema of the respiratory system. Some congenital heart diseases can also lead to opaque lips, such as tetralogy of Fallot and hypertrophic cardiomyopathy, which can be diagnosed by cardiac ultrasound. When you come from a low altitude area to a high altitude area, some people will also have opaque lips, for example, when you go from a plain area to the Qinghai-Tibet Plateau area. As soon as you return to a lower altitude area, the symptoms of black lips will be relieved. There are many causes of opaque lips, which need to be determined based on various tests.