Lip "skin" is very unique. It actually consists
primarily of mucous membrane, which has fewer and different
glands than ordinary skin. the lip is also unlike other
skin in that the outer layer (stratum corneum) is extremely
thin or completely absent in most people. Lips also
have almost no melanin, the natural pigment in skin that helps
screen out the sun's harmful rays.
As a result of the properties of lip skin, moisture rapidly evaporates
from the lips, causing them to dry out very easily. This dryness frequently results in chapping and cracking,
and increases the risk of inflammation, infection and burning.
Your lips' natural tendency toward dryness and chapping is aggravated
by the fact that they are more prominent than almost any other
part of your body--and most of the time they are unprotected
by clothing and fully exposed to the elements. While
exposure to sun, wind and cold can obviously speed the rate
of moisture loss, your lips aren't even safe indoors.
They can suffer from lack of moisture in centrally heated
or air-conditioned rooms in which the relative humidity is
low.
Environmental factors are clearly one of the most important causes of lip
dryness, but they are by no means the only culprit.
For instance, many people's lips can also become dry when
the common winter cold or flu strikes. This lip dryness
happens because of people's tendency to breathe through their
mouth when they get sick, inadvertently drying out their lips. Lip irritation can even be caused by certain types of food,
cosmetics and cigarette smoke.
For some words of advice on ensuring the
health of your lips in the face of the various forces
of dryness, follow this link.
