Editing Itch (section)

== Signs and symptoms ==
Pain and itch have very different behavioral response patterns. Pain elicits a withdrawal reflex, which leads to retraction and therefore a reaction trying to protect an endangered part of the body. Itch in contrast creates a [[scratch reflex]], which draws one to the affected skin site. Itch generates stimulus of a foreign object underneath or upon the skin and also the urge to remove it. For example, responding to a local itch sensation is an effective way to remove insects from one's skin.

Scratching has traditionally been regarded as a way to relieve oneself by reducing the annoying itch sensation. However, there are [[hedonic]] aspects to scratching, as one would find noxious scratching highly pleasurable.<ref name=ikoma/> This can be problematic with [[chronic (medicine)|chronic]] itch patients, such as ones with [[atopic dermatitis]], who may scratch affected spots until they no longer produce a pleasant or painful sensation, instead of when the itch sensation disappears.<ref>{{cite journal |vauthors=Karsak M, Gaffal E, Date R, Wang-Eckhardt L, Rehnelt J, Petrosino S, Starowicz K, Steuder R, Schlicker E, Cravatt B, Mechoulam R, Buettner R, Werner S, Di Marzo V, Tüting T, Zimmer A |display-authors=3 |title=Attenuation of allergic contact dermatitis through the endocannabinoid system |journal=Science |volume=316 |issue=5830 |pages=1494–1497 |date=June 2007 |pmid=17556587 |doi=10.1126/science.1142265 |s2cid=37611370 |bibcode=2007Sci...316.1494K}}</ref> It has been hypothesized that motivational aspects of scratching include the frontal brain areas of reward and decision making. These aspects might therefore contribute to the compulsive nature of itch and scratching.<ref name=ikoma/>

=== Contagious itch ===
Events of "[[Contagious disease|contagious]] itch" are very common occurrences. Even a discussion on the topic of itch can give one the desire to scratch. Itch is likely to be more than a localized phenomenon in the place one scratches. Results from a study showed that itching and scratching were induced purely by visual [[Stimulus (physiology)|stimuli]] in a public lecture on itching.<ref>[citation needed]</ref> The sensation of pain can also be induced in a similar fashion, often by listening to a description of an injury, or viewing an injury itself.

There is little detailed data on central activation for contagious itching, but it is hypothesized that a human [[mirror neuron]] system exists in which one imitates certain motor actions when they view others performing the same action. A similar hypothesis has been used to explain the cause of contagious [[yawning]].<ref name=ikoma/>

=== Itch inhibition due to pain ===
Studies done in the last decade have shown that itch can be inhibited by many other forms of painful stimuli, such as [[Noxious stimulus|noxious]] heat,<ref>{{cite journal |vauthors=Yosipovitch G, Fast K, Bernhard JD |title=Noxious heat and scratching decrease histamine-induced itch and skin blood flow |journal=The Journal of Investigative Dermatology |volume=125 |issue=6 |pages=1268–1272 |date=December 2005 |pmid=16354198 |doi=10.1111/j.0022-202X.2005.23942.x |doi-access=free}}</ref> physical rubbing/scratching, noxious chemicals, and [[electric shock]].<ref>{{cite journal |vauthors=Ward L, Wright E, McMahon SB |title=A comparison of the effects of noxious and innocuous counterstimuli on experimentally induced itch and pain |journal=Pain |volume=64 |issue=1 |pages=129–138 |date=January 1996 |pmid=8867255 |doi=10.1016/0304-3959(95)00080-1 |s2cid=25772165}}</ref>