Why do millions suffer from dry chapped lips when the weather turns cold? The reason can be found in the structure of the lips themselves. The lips' structure is actually different than other skin. As shown in the diagram to the left, lips do not have the same protective outer layer, or stratum corneum, found in other skin; nor do lips have the same amount of oil and sweat glands. Sweat glands add moisture to skin, but the lips' only source of moisture is saliva inside the mouth. Thus, harsh winter wind, cold, sun and dryness--indoors and outdoors--make lips more susceptible to dryness and a vulnerable target for chapping.