The human lips (labia oris) is the junction between the outer facial skin and inner buccal mucosa that lines the mouth cavity. The color of skin is determined by the amount of natural pigment known as melanin. Melanocytes are specialized pigment cells that produce melanin in smaller quantities than elsewhere on the skin. The lips also have melanin but to a much lesser degree than the rest of the skin.
This lower quantity of melanin is genetically determined but is further regulated by exposure to ultraviolet light mainly from sunlight and less frequently from tanning. Combined with its fewer layers of skin than the rest of the face, the color of the lips is also largely dependent on the underlying tissue color and blood flow. This is the reason that the lips are a pink to red color.
On the other hand, black lips or having very dark colored lips is contributed by several factors and can be used as indicators for certain conditions that are happening inside the body. Though very rare, there are certain severe medical conditions that can cause the lips to turn a darker shade or even black like having cancer. It can be contributed by living a modern lifestyle, certain eating habits and some medications. There are people that naturally have black lips or dark-colored lips.
Causes of Black Lips/Darker Lips:
1. The major cause of black lips is smoking.
2. Constant biting and licking of the lips.
3. Frequent drinking of hot beverages that contain caffeine like coffee and tea.
4. Low vitamin B levels.
5. Change in hormonal levels that are contributed by age, infection, diseases and other factors.
6. Certain toothpaste brands and lip medications along with other kinds of medications used to treat diseases and infection.
7. Allergic reactions and injuries.
8. Iron levels of the body can contribute in making the lips black. When there is an increase or overflow of iron levels in the body, this will usually show in the lip area and can be observed when it turns black.
9. Improper dental fixtures can also cause lips to darken but very rarely.
There are several treatment options and products like LipIce Lip Balm which can be handy to help lighten the lips and remove the dark discoloration.