An eyelash (also called lash) (Neo-Latin: cilium, plural cilia) is one of the hairs that grows at the edges of the top and bottom eyelids, spanning outwards and away from the eyes.

[1] Eyelashes serve to protect the eye from debris, dust, and small particles, and are highly sensitive to touch, thus providing a warning that an object (such as an insect or lint) is near the eye, which then reflexively closes or flutters to rid the area of the object.

The word eyelash is a compound consisting of the words eye, referring to the eye which the lashes surround and protect; and lash, referring to the braided cord of a whip or to the act of stroking with a whip.

Eyelash length is closely linked to the width of the eye, with the lashes typically growing to one-third the width of the eye as an evolutionary adaptation to reduce tear film evaporation and dust deposition.

Lashes longer or shorter than one-third the width of the eye have been shown to have reduced efficacy in serving their function.

[13] Eyelashes grow outwards from both upper and lower eyelids, with varying degrees of curl.

Prominent, luscious eyelashes have long been considered a sign of beauty in many cultures, almost universally,[23] and as such are highly coveted, particularly by women.

[25] Despite not varying by sex and not being a secondary sex characteristic, long, prominent lashes are frequently considered a feminine trait, with studies showing that women possessing longer lashes are perceived as healthier and more feminine.

[26] Nevertheless, long lashes are regarded as an attractive facial feature in both males and females.

[27] Nonetheless, an average length eyelash is considered the most attractive across Asian, Indian, Black and White faces.

[28] Ancient Romans considered long eyelashes a component of aesthetically ideal eyes.

Pliny the Elder wrote that eyelashes fell out from sexual excess, so women desired long lashes as a symbol of chastity.

[34] Latisse was introduced in the first quarter of 2009 by Allergan as the first drug to receive FDA approval for eyelash growth.

Latisse is a solution of bimatoprost, a prostaglandin analog and the active component of the glaucoma medication Lumigan.

[36] Cosmetic companies have recently relied on scientific research of prostaglandins and the Wnt/b-catenin signaling pathways to develop eyelash products.

[37] Some cosmetic brands have begun using peptides in their formulation rather than prostaglandins because of regulatory rules in places like Canada and California.