Dry skin is a predomonant trait of a Vata constitution. Even in normal people, Vata causes dryness of the skin when it is vitiated due to seasonal influences. This dryness may even extend to the mucous membranes covering the lips and thus cause cracking. Dryness of the skin and the mucous membranes is also caused by certain illnesses like fever.
An oil massage is a simple yet well-known remedy to treat dry skin. For better results, you may add a few drops of glycerine to the oil just before application.
Clarified butter or milk cream are good for cracked lips. Apply them for a couple of days just before going to bed.
Ayurvedic Medicines for Dry Skin by Dabur