There are many reasons for the black lips of boys, such as physiological factors, cardiopulmonary insufficiency, renal insufficiency and so on. 1. Physiological factors: boys born with black skin, or long-term smoking, etc., may lead to the phenomenon of boys with black lips, is a normal physiological phenomenon. 2. Cardiorespiratory insufficiency: boys suffering from chronic obstructive pulmonary disease, cardiac insufficiency and other diseases, can lead to ventilation dysfunction, low oxygen content in the blood, and so on, so that the lips lack of oxygen, which may lead to the boys lips black. 3. Renal insufficiency: renal insufficiency in boys can also lead to the phenomenon of pigmentation on the edge of the lips, thus leading to the phenomenon of black lips in boys. Many reasons that lead to the black lips of boys, if you exclude physiological factors, it is recommended that boys go to the hospital in time to improve the examination, a clear diagnosis, to give standardized treatment, do not ignore the symptoms, to take it lightly.