Blackness around the lips is caused by the following factors: 1, the most common factor is the lack of oxygen in the body, when the oxygen supply is inadequate, such as the body’s blood oxygen saturation is reduced, carbon dioxide partial pressure is too high or blood oxygen saturation is seriously inadequate, there will be clinical symptoms and performance of blackness around the lips, because diseases such as pulmonary insufficiency, pulmonary hypertension or chronic pulmonary heart disease, emphysema will appear when the clinical symptoms and performance of blackness around the lips. The above clinical symptoms also occur in patients with obvious cardiac insufficiency, because the coronary arteries supplying blood to the heart are ischemic and lead to insufficient blood flow to the body, which will produce clinical symptoms and manifestations of significant darkness around the lips. 3. rare diseases, rare diseases such as chemical contamination poisoning or food poisoning, also show clinical manifestations of darkness around the mouth.