Lip Skin does not have the same protective outer layer found in other type of skin. Unlike ordinary skin, lip tissue is mucous membrane. The outer layer of the lip (or stratum corneum) is extremely thin or even completely absent in most people. As a result, moisture evaporates from the lips much faster than from ordinary skin causing lips to dry out easily. This dryness frequently results in chapping and cracking, and increases the risk of inflammation, infection and burning sensations.