Cucumber slices have been associated with beauty regimens for awhile now. The image of a spa patron with his or her face covered with a skin mask and a slice of cucumber over each eye is a ubiquitous one. Cucumber slices have been shown to be effective in enhancing the beauty of skin by reducing the appearance of under-eye swelling. What works on the sensitive skin beneath the eyes can also work for dry lips.
Cucumber is composed of mostly water -- more than 90 percent -- which means it can serve as a delivery vehicle for H2O [source: Chow]. The water in raw cucumber slices can help restore moisture in lips on its own, but cucumber has other ingredients that can promote the health of lips as well. The vegetable has a significant amount of ascorbic acid, known more familiarly as vitamin C. Ascorbic acid promotes the production of collagen, a connective protein that gives structure and resilience to skin tissue. Cucumber also contains caffeic acid, an antioxidant that suppresses the generation of free radicals by ultraviolet radiation (UV) from the sun [source: Yamada, et al].
Combined into cucumber slices applied topically to the lips, the water and caffeic and ascorbic acids moisturize lips, promote lip fullness and protect from sun damage. Not bad from a vegetable you can get for less than a buck at the local market.