Lip licking is an unhealthy behavior that darkens your lips and the area around your mouth. Saliva contains enzymes that aid in the digestion of food, and licking your lips frequently can irritate the thin, sensitive skin, causing it to darken in color. One of the major reasons for lips turning dark is due to accumulation of dead cells. Scrubs prove effective in removing dead skin and making them smooth and soft again. Mix a tablespoon of sugar and one tablespoon honey, and gently massage it on your lips for one minute. After a few minutes, wash it off. Sugar not only exfoliates the lips but is also rich in antioxidants that protect the lips from the sun. Sugar also contains glycolic acid that protects the lips from environmental toxins. Honey contains enzymes that lighten the colour of the lips.