Mascara is a type of cosmetic applied to the eyelashes. It serves to thicken and define the eyelashes and may also color, lengthen, or curl them, depending upon the type of mascara. Usually, mascara is a liquid cosmetic sold in a tube and applied with a round brush called a wand. However, cream and cake mascaras also exist. Cake mascara was the only form available before the tube-and-wand variety was introduced in 1957.

Cosmetics used to darken the eyelashes and eyebrows are ancient in origin. The Kama Sutra, a 4th century CE Sanskrit text on the art of love and lovemaking, includes a mascara recipe. Eugene Rimmel, a French perfume magnate, was the first to commercially market mascara in the 1830s, and his name is still the word for "mascara" in some languages.

The next innovation in mascara was in 1913, when T. L. Williams, the founder of Maybelline cosmetics, combined coal dust and Vaseline to produce cake mascara. William's product was applied to the lashes with a moistened brush. Subsequent versions of cake mascara were composed of wax and colorant. Helena Rubenstein pioneered the now ubiquitous tube-and-wand mascara in 1957.

Today, there are a truly staggering amount of mascara products on the market. There are clear mascaras and primers that thicken the lashes without adding color, as well as colored mascaras in outrageous shades such as lime green, gold, and pink. Waterproof mascaras prevent smudging, help the lashes retain their curl, and reduce the tendency for lashes to clump together. Volumizing and lengthening mascaras include nylon or rayon fibers that act as temporary extensions for the eyelashes. Some mascara products contain conditioners like pro-vitamin B5, more commonly seen in hair conditioners.

Mascara can be applied to all the eyelashes, but some people use it only above the eye. Wiggling the applicator brush at the base of the lashes can help make the lashes appear fuller, and moving the brush in a zig-zag pattern to the end of the lashes can help reduce clumping. If you wish to apply a second coat, do so before the first coat is dry to further avoid clumping lashes.

Because mascara is used on such a delicate part of the body, it is important not to keep a tube around too long, as using old mascara can introduce bacteria into the eyes and cause serious health problems. Most commercial mascaras include an antibacterial agent that lasts about six weeks, and anything over four months old should definitely be replaced. If your eyes feel irritated or if you notice any change in the texture or smell of your mascara, do not continue to use it.