An eyelash or simply lash is one of the hairs that grow at the edge of the eyelid. Eyelashes protect the eye from debris and perform some of the same function as whiskers do on a cat or a mouse in the sense that they are sensitive to being touched, thus providing a warning that an object (such as an insect or dust mite) is near the eye (which is then closed reflexively).
[edit] Human eyelashes
The eyelashes of the embryo develop between the 7th and 8th week. Eyelashes take about seven to eight weeks to grow back if pulled out. Their color may differ from that of the hair, although they tend to be dark on someone with dark hair and lighter on someone with light hair.
The follicles of eyelashes are associated with a number of glands known as the Glands of Zeis and the Glands of Moll.
[edit] Cosmetics
Long eyelashes are considered a sign of femininity in many cultures. Accordingly, some women seek to enhance their eyelash length artificially. See eyelash extensions. On the other hand, Hadza women pluck their eyelashes completely.
Kohl has been worn as far back as the Bronze Age to protect and enhance lashes. In Ancient Egypt it was used as well by the wealthy and the royal to protect their eyes from the sand, dust and bugs.
Modern eye makeup includes mascara, eyeliner, eye putty, and eye shadow to emphasize the eyes. The twentieth century saw the beginning of convincing-looking false eyelashes, popular in the 1960s.
Permanent eyelash tints and eyelash extensions have also become popular procedures, even in fairly basic salons.
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 weak concentration of bimatropost, the active component of the glaucoma medication Lumigan. According to Allergan, noticeable eyelash growth occurs within 16 weeks. Growth is reported to occur primarily on the upper eyelashes.
[edit] Health
There are a number of diseases or disorders involving the eyelashes:
- Madarosis is the loss of eyelashes
- Blepharitis is the irritation of the lid margin (where eyelashes join the eyelid). Eyelids are red and itching. The skin often becomes flaky. The eyelashes may fall.
- Distichiasis is the abnormal growth of lashes from certain areas of the eyelid.
- Trichiasis is ingrown eyelashes
- Eyelashes may become infested with crab louse parasites
- An external hordeolum, or stye, is a purulent inflammation of infected eyelash follicles and surrounding sebaceous (Zeis) and apocrine (Moll) glands of the lid margin.
- Trichotillomania is a disorder that urges the sufferer to pull out scalp hair, eyelashes, etc.
- Demodex folliculorum (or the demodicid), is a small mite that lives, harmlessly, in eyelash and other hair follicles and around 98% of people have these mites living on them. Occasionally they can cause blepharitis.
Eyelash and eyebrow transplant surgeries may be help to reconstruct or thicken lashes or eyebrow hair.
[edit] Nonhumans
A horse's eye, showing lashes
Lashes, being hair, are found in mammals. Camels' lashes are remarkably long and thick. Horses, cows, and also ostriches, (vestigial feathers without barbs) feature eyelashes as well.
Inherited eyelash problems are common in some breeds of dogs.
Eyelash vipers show a set of modified scales over the eyes which look much like eyelashes.
Hornbills have prominent feather eyelashes, an uncommon feature in birds.
[edit] References
