Lips Appreciation Day

What the day is

Lips Appreciation Day is observed on March 16. Lips are an unusual piece of anatomy, and most of what makes them distinctive also makes them fragile.

Origin and background

The red part of the lip is a transitional zone between facial skin and the lining of the mouth, and it is built differently from both. The outer layer is far thinner than ordinary skin, it contains very little of the pigment that protects against ultraviolet light, and crucially it has no sebaceous glands and no sweat glands, so it produces none of the oily film that keeps the rest of the face from drying out. The color comes from blood vessels showing through that thin covering, which is also why lips pale when someone is cold or has lost blood.

Everything follows from that. Lips chap because they cannot moisturize themselves and lose water faster than surrounding skin. Licking them makes it worse, since saliva evaporates and takes surface moisture with it, and contains digestive enzymes that irritate. And the lower lip in particular is a common site for sun-related skin damage precisely because it lacks pigment and is angled toward the sky, which is why dermatologists recommend a lip balm with sun protection rather than treating it as optional.

The sensitivity is the other half. Lips carry a very high density of touch receptors and occupy a disproportionately large share of the brain's sensory map, out of all proportion to their size, which is why they detect textures and temperatures the fingers miss.

They are also central to speech, forming the consonants that require closing the mouth entirely.

How to take part

• Use a balm with sun protection, particularly outdoors in winter.
• Stop licking chapped lips, which is what keeps them chapped.
• Check for a patch that does not heal, which is worth showing a doctor.
• Drink water. Lips show dehydration before most other tissue.
• Look up the sensory map and see how much space they occupy.