Lip discoloration is caused by a number of factors including anemia, cyanosis, melasma, too much sun exposure, consumption of excessively hot food, high intake of caffeine, licking and biting of lips, vitamin B deficiency, high levels of iron, hormonal changes, allergies, excessive pigmentation, dry lips or jaundice. Discoloration of lips can also sometimes be a hidden symptom of cancer in some cases.
Alcohol abuse, regular narcotic use and cigarette smoking can also cause the discoloration of lips. In most cases, it is associated with brownish-gray to dark brown hues. Labial melanotic macules is another condition that causes benign dark spots on lips, which are common in women aged 40 to 50 years, as stated in a study conducted by Dr. S. Sutera in 2013 at the University of Milan. Although lips do not turn fully black, they turn yellowish or bluish when discolored due to systemic diseases, chemical damage or lifestyle factors.