Editing Hair (section)

===Touch sense===
Displacement and vibration of hair shafts are detected by hair follicle nerve receptors and nerve receptors within the skin. Hairs can sense movements of air as well as touch by physical objects and they provide sensory awareness of the presence of [[ectoparasites]].<ref>{{Cite journal | doi = 10.1098/rsbl.2011.0987| pmid = 22171023| title = Human fine body hair enhances ectoparasite detection| journal = Biology Letters| volume = 8| issue = 3| pages = 358–61| year = 2011| last1 = Dean | first1 = I.| last2 = Siva-Jothy | first2 = M. T. | pmc=3367735}}</ref> Some hairs, such as [[eyelash]]es, are especially sensitive to the presence of potentially harmful matter.<ref>{{cite web|title=Neuroscience for Kids – Receptors|url=http://faculty.washington.edu/chudler/receptor.html|access-date=18 February 2015|publisher=Faculty.washington.edu}}</ref><ref>{{cite web|title=hair biology – functions of the hair fiber and hair follicle|url=http://www.keratin.com/aa/aa031.shtml|access-date=18 February 2015|publisher=Keratin.com|archive-date=30 March 2017|archive-url=https://web.archive.org/web/20170330014433/http://www.keratin.com/aa/aa031.shtml|url-status=dead}}</ref><ref>{{cite journal|pmid=4811387|last1=Sabah|first1=NH|year=1974|pages=256–7|issue=2|volume=36|title=Controlled stimulation of hair follicle receptors|journal=Journal of Applied Physiology|doi=10.1152/jappl.1974.36.2.256}}</ref><ref>{{Cite journal | doi = 10.1016/S0047-2484(85)80090-7| title = The evolution of human skin(?)| journal = Journal of Human Evolution| volume = 14| pages = 3–22| year = 1985| last1 = Montagna | first1 = W.| issue = 1| bibcode = 1985JHumE..14....3M}}</ref>
[[File:Jeremy Cadot's eyebrow.jpg|thumb|Eyebrows prevent sweat, water, and other debris from above from falling down into the eye.]]
[[File:Closed human eye, superior view.jpg|thumb|Eyelashes are hairs on the edges of the eyelids that catch dust and dirt when the eye is blinked.]]

====Eyebrows and eyelashes====
{{main|Eyebrows|Eyelashes}}

The [[eyebrow]]s provide moderate protection to the [[eye]]s from [[dirt]], [[sweat]] and [[rain]]. They also play a key role in non-verbal [[communication]] by displaying emotions such as sadness, anger, surprise and excitement. In many other mammals, they contain much longer, whisker-like hairs that act as tactile sensors.

The [[eyelash]] grows at the edges of the eyelid and protects the eye from dirt. The eyelash is to humans, camels, horses, ostriches etc., what [[whiskers]] are to [[cat]]s; they are used to sense when dirt, [[dust]], or any other potentially harmful object is too close to the eye.<ref name="Thumbprints - The Human Eyelash.">{{cite web |url=http://ion.asu.edu/liv41_eyelash/liv41_thumb.htm |title=Images of Nature |publisher=Ion.asu.edu |access-date=18 February 2015 |url-status=dead |archive-url=https://web.archive.org/web/20060508183602/http://ion.asu.edu/liv41_eyelash/liv41_thumb.htm |archive-date=8 May 2006 }}</ref> The eye reflexively closes as a result of this [[sensation (psychology)|sensation]].

Eyebrows and eyelashes do not grow beyond a certain length (eyelashes are rarely more than 10&nbsp;mm long). However, [[trichomegaly]] can cause the lashes to grow remarkably long and prominent (in some cases the upper lashes grow to 15&nbsp;mm long).