Vermilion border  the exposed red portion of the upper and lower lips. It extends from the junction of the lips with the surrounding facial skin on the exterior to the labial mucosa within the mouth.

Actinic chelitis is caused by chronic and excessive exposure to the ultraviolet radiation in sunlight. There is thickening whitish discoloration of the lip at the border of the lip and skin. There is also loss of the usually sharp demarcation between the red of the lip and the normal skin (vermilion border). This condition is considered premalignant and may lead to squamous cell skin cancer.

Photo from graphics8.nytimes.com

Tags: skin cancer, vermilion border