Facts about your lips you probably didn’t know

Your lips are a transition zone. The red part, called the vermilion, is where the skin of your face meets the moist lining inside your mouth. It looks like skin, but it behaves very differently.

Its protective outer layer is only a few cell layers thick, far fewer than on the rest of your face. That’s also why lips look red: with so little covering them, the blood vessels underneath show through.

Thin, exposed and constantly in use. That combination explains almost everything about how lips behave.

Lips have no sweat glands and almost no oil glands. Most of your skin uses oil to form a protective film. Lips can’t make enough of it.

They also lose water faster than most of the skin on your face, which is why they’re usually the first place to feel dry in winter or on a plane.

Licking them makes it worse. Saliva evaporates quickly and takes moisture with it, and it contains digestive enzymes that can irritate the skin.

Lips are packed with nerve endings and are among the most touch-sensitive areas you have, which is why even a tiny crack can feel so uncomfortable.

They also contain very little melanin, the pigment that helps protect skin from the sun. That means lips can burn easily, even when the rest of your face doesn’t.

Thin, sensitive and barely protected from the sun. Lips need more care than they usually get.

Your lip print is unique. The pattern of lines on your lips is individual enough that forensic scientists study it as a form of identification, a field called cheiloscopy.

Humans are unusual among primates. Our lips turn outward, which makes the red part visible. In most other primates, it stays tucked inside.

Some medications affect lips more than you’d expect. Certain acne medications, such as isotretinoin, are well known for leaving lips very dry, and many other common medicines can do it too.