• Trauma or injury. A bruise can form on one or both lips following an injury. This can cause your lips to be partly or entirely purple or other dark tones.
• Heat from smoking that cause lips to turn dark in color
• Lack of Vitamins such as B12
• Dehydration
• Hyperpigmentation is also called Melasma( abnormal increase of the melanin on the skin and lips)
• Thyroid disorders
• Certain use of medications
• Too much caffeine consumption
• Lip sucking/biting
• Allergic reactions to foods, toothpaste, lipstick or cosmetics
• Lips that turn blue or darker in color may be a sign that there’s not enough oxygen available from the bloodstream
• Certain chemicals in lipsticks, balms and colored lip creams may also cause rashes and hyperpigmentation