If the lips appear black and purple, a drop in oxygen levels in the blood is considered, and the most common causes are long-term chronic lung diseases such as chronic obstructive pulmonary disease and bronchial asthma. These diseases can cause impaired oxygen exchange in the lungs, leading to the appearance of decreased blood oxygen, and the lips, as well as the nail beds, may be bruised. In addition, many congenital heart diseases can have the same symptoms as described above, the most common being atrial septal defects, ventricular septal defects, and arterial catheterization. In these diseases, if a right-to-left shunt occurs at the site of the defect, resulting in the mixing of venous blood with arterial blood, a definite decrease in blood oxygenation will occur, which will be manifested by a dark purple coloration of the face, and the lips and nail beds will be more obvious.