Vitamin B and zinc defiencies makes the lips to lose its moisture. Some certain lip balms are not good or healthy for the lips, because it sucks the moisture out of the skin and may cause the lips to dry; lack of these Vitamins leads to dry lips.
Also picking and licking the lips makes it dry, by doing so it gets worse by the day. The human body can not produce these Vitamins on its own, that has to be gotten from other sources, such as what we consume .
In other to have a healthy lips without any crack, eat healthy and keep the lips lubricated with the right products that the lips can retain!