Smudge-proof eyeliner provides a line of defense against makeup smearing throughout the day and producing what some call "raccoon eyes," in which the eyes become unattractively ringed with black globs of makeup. Wearing waterproof eyeliner and mascara is one way to ensure smudge-proof makeup.
Eyeliner usually smudges due to oil on the skin. When this occurs, the eyes look less defined and attractive. Smudge-proof eyeliners tend to show a consistently smooth glide and some resistance when applied. Eyeliner can be made more smudge-proof by using makeup primer under the eyeliner to prevent oil build-up. Setting the eyeliner with powder also helps it to stay in place.