Solar cheilitis primarily affects which part of the lip?

Solar cheilitis, also known as actinic cheilitis, primarily affects the vermilion border of the lips. This condition results from prolonged exposure to ultraviolet (UV) light, leading to changes in the texture and appearance of the vermilion, which is the pink-red area of the lips. Symptoms often include dryness, cracking, and a rough texture, and can also lead to more serious conditions, including squamous cell carcinoma in advanced cases.

The labial mucosa refers to the inner lining of the lips, which is not the primary site affected by solar cheilitis. The oral cavity encompasses the entire mouth area, including the gums, tongue, and inner cheeks, and while it may be affected by different conditions, it is not specifically impacted by solar cheilitis. The philtrum, which is the vertical groove between the upper lip and the nose, is not where the effects of solar exposure manifest significantly, thus making the vermilion the correct focus for this condition.