Cyanosis is a manifestation of increased reduced hemoglobin in the blood, which causes cyanotic changes in the skin and mucous membranes. This kind of manifests mainly in the parts with thinner skin, less pigment and richer capillaries, such as the parts of the mouth and lips. Diseases that cause purple lips can include obstructive emphysema, diffuse interstitial lung fibrosis, pulmonary stasis, pulmonary edema, acute respiratory distress syndrome, pulmonary embolism, pulmonary hypertension, obstruction of the larynx, trachea and bronchi, pneumonia, and some congenital heart diseases, such as tetralogy of Fallot and Eisenmenger syndrome. There are also some diseases, like severe shock, pericardial tamponade, right heart failure, etc., which can also cause bruising of the lips.