An eyelash is one of the hairs that grow at the edge of the eyelid that serve to protect the eye from debris. They also are considered by many to be an important element of beauty. Many women (and now some men) seek ways to make their eyelashes longer, thicker, darker, and lusher.

Eye liner is a cosmetic used to define the eyes.

Mascara is a cosmetic used to darken, lighten or colour lashes, also it can be used to thicken, lengthen and define eyelashes.

The active ingredients of mascaras are pigments in a moisturizing base. Waterproof liquid mascaras contain heavy, oil-based moisturizing formulas to which acrylates and shellacs are often added. These serve to thicken mascaras and make them more rain- and tear-resistant. So called conditioning mascaras generally have water-based moisturizing formulas and tend to be less resistant. Removal of mascara usually requires soap and water or cleansing lotions containing mineral oil.

Temporary stinging and burning of the eyes or lids during eye cosmetic application is frequently caused by evaporation of the product's volatile ingredients, such as mineral spirits, isoparaffins, and alcohol. Irritation may also result from the presence of such troublemakers as propylene glycol or soap emulsifiers. Some people who are unable to tolerate water-based mascaras may be able to use waterproof products, and vice versa.

Although it is true that loose eyelashes often fall out when mascara is applied, these hairs do grow back. Mascara does not cause permanent loss of eyelashes. In fact, with proper use, mascaras cause few problems.

There are, however, two caveats:

First, contact lens wearers should avoid lash-extending mascaras. These products generally contain numerous, very fine particles of rayon that can become trapped under contact lenses, causing irritation or even scratching of the eye's delicate cornea.

Second, the concentration of preservatives in mascaras purposely has been kept low so as not to irritate the eyes, but this also means that the products do not have a long shelf life, and they are not contamination resistant. Two good rules of thumb: Never share mascara and discard mascara after three or four months.

Learn more about cosmetics, including mascaras from Nelson Novick, M.D.

Latisse® is a new prescription medication for the treatment of inadequate or insufficient eyelashes, growing them longer, fuller, and darker.