Vermillion border

Vermilion border
Erythema above the lips, making it more difficult to distinguish the vermilion border.
This left cheek incision extends from the left commissure towards the left ear and it breaches the vermilion border (click to see close-up). In order to maintain aesthetics as best possible, the first suture was placed at or near the vermilion border to ensure a contiguous line upon healing.
Details
Identifiers
Latin	pars intermedia labiorum oris
Code	TH H03.04.01.0.00010
Anatomical terminology []

The vermilion border (sometimes spelled vermillion border) is the normally sharp demarcation between the lip and the adjacent normal skin. It is thus the edge (border) of the red (vermilion) of the lip. It represents the change in the epidermis from highly keratinized external skin to less keratinized internal skin. It has no sebaceous glands, sweat glands, or facial hair.

There are two reasons for the border being red:

The vermilion border is important in dentistry and oral pathology as a marker to detect disease, such as in actinic cheilitis.

A vermilionectomy (sometimes spelled vermillionectomy) is the surgical removal of the vermilion border. It is sometimes performed to treat carcinoma of the lip.