Eyelashes (from Latin cilium) are hairs located on the free edges of the eyelids.

Eyelashes are hairs that are part of the integuments, like hair and nails.

Position. The eyelashes start on the free edges of the 4 eyelids (1). With an average length of 8 to 12 mm, the eyelashes of the upper eyelids number 150 to 200 per eyelid. The eyelashes of the lower eyelids are fewer and shorter. From 50 to 150 eyelashes are arranged on each eyelid with a length of 6 to 8 mm on average.

Structure. The eyelashes have the same structure as the bristles. They consist of two parts (2):

• The stem is the elongated part made up of keratinized cells, which are continually being renewed. These cells contain pigments which give the specific color to the eyelashes. The oldest cells are on the free end of the hair.
• The root is the end of the hair implanted deep in the dermis. The enlarged base forms the hair bulb which contains the nutritive vessels, notably allowing cell renewal and hair growth.

Innervation. Hair follicles, the cavities in which the eyelashes reside, have many nerve endings (1).

Ancillary glands. Different glands are attached to the eyelashes, including the sweat glands and the sebaceous glands. The latter secrete an oily substance that lubricates the eyelids and the eye (1).

Protective role / Blinking eyes. The eyelashes have hair follicles with many nerve endings, to warn and protect the eyes in case of danger. This phenomenon will induce reflex blinking of the eyes (1).

Eyelash abnormalities. Certain pathologies can cause abnormalities in the growth, pigmentation, direction or position of the eyelashes (3).

• Growth abnormalities. Certain pathologies can affect the growth of the eyelashes such as hypotrichosis, corresponding to a stop in the growth of the eyelashes; hypertrichosis, constituting a growth of the eyelashes in thickness and too great a length; or madarosis with absence or loss of eyelashes.
• Pigmentation abnormalities. Eyelash pigmentation problems can be linked to certain pathologies such as leukotrichia, defined by the absence of ciliary pigmentation; poliosis or canities, denoting respectively a whitening of the eyelashes and a total whitening of the hairs on the body.
• Directional and positional anomalies. Certain pathologies can modify the direction or the position of the eyelashes such as distichiasis, developing a double row of eyelashes; or trichiasis where the eyelashes rub abnormally against the eye.

Alopecia. Alopecia refers to a partial or total loss of hair or body hair.4 Its origin may be linked to genetic factors, age, a disorder or disease, or even repeated epilation. This results in two types of alopecia: non-scarring where hair regrowth is possible since there is no damage to the hair follicles; and scars where no regrowth is possible because the hair follicles are completely destroyed.

Pelade. Alopecia areata is a disease characterized by hair loss or patches of hair. It can affect only certain parts of the body or the whole. Its cause is still poorly understood, but some studies suggest an autoimmune origin. (5)

Drug treatments. Depending on the origin of the hair loss, certain treatments may be prescribed such as anti-inflammatory drugs (corticosteroids), hormonal treatments or vasodilator lotions.

Surgical treatment. Depending on the pathology diagnosed, surgical treatment may be implemented.

Dermatological examination. In order to identify the origin of the pathology affecting the eyelashes, a dermatological examination is carried out.

Aesthetic symbol. Eyelashes are associated with femininity and the beauty of the gaze.