If the patient presents with prolonged darkening and blackening of the lips. Firstly, cardiogenic diseases such as coronary artery disease, unstable angina, myocarditis, heart valve disease, hypertensive heart disease, congenital heart disease, hypertrophic obstructive heart disease, rheumatic heart disease, etc. will have insufficient blood supply to the coronary arteries, which will lead to long-term darkening of the lips when the blood supply and oxygen supply are insufficient. Secondly, chronic respiratory diseases such as chronic emphysema, chronic bronchitis, chronic bronchial dilatation, chronic obstructive pulmonary disease, pulmonary hypertension will also lead to a decrease in arterial blood oxygen saturation, reduced partial pressure of oxygen and high partial pressure of carbon dioxide will also cause long-term oozing of the lips. Finally, if the patient has chronic poisoning, such as chronic heavy metal poisoning will also have the above clinical symptoms.