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3,605 bytes added ,  22:28, 4 September 2011
Created page with 'File:lighterstill.jpgright|frame ==Origin== Latin ''irrītāt''-, participial stem of ''irrītā-re'' to incite, [[exc...'
[[File:lighterstill.jpg]][[File:How_to_control_anger_and_irritation_2.jpg|right|frame]]

==Origin==
[[Latin]] ''irrītāt''-, participial stem of ''irrītā-re'' to incite, [[excite]], provoke
*[http://en.wikipedia.org/wiki/15th_century 15th Century]
==Definitions==
*1: to provoke impatience, [[anger]], or displeasure in : annoy
==Description==
'''Irritation''' or ''exacerbation'', in [[biology]] and [http://en.wikipedia.org/wiki/Physiology physiology], is a [[state]] of [http://en.wikipedia.org/wiki/Inflammation inflammation] or [[painful]] [[reaction]] to [http://en.wikipedia.org/wiki/Allergy allergy] or cell-lining damage. A [[stimulus]] or [[agent]] which induces the state of irritation is an irritant. Irritants are typically [[thought]] of as [[chemical]] agents but [[mechanical]], thermal ([[heat]]), and radiative [[stimuli]] can also be irritants. Irritation also has non-clinical usages referring to bothersome [[physical]] or [[psychological]] [[pain]] or discomfort.
''
Chronic irritation'' is a medical [[term]] [[signifying]] that afflictive [[health]] conditions have been present for a while. There are many disorders that can cause chronic irritation, the [[majority]] involves the skin, vagina, eyes and lungs.

In higher [[organisms]], an [http://en.wikipedia.org/wiki/Allergy allergic response] may be the cause of irritation. An allergen is defined distinctly from an irritant, however, as allergy requires a specific [[interaction]] with the [http://en.wikipedia.org/wiki/Immune_system immune system] and is thus dependent on the (possibly [[unique]]) [[sensitivity]] of the organism involved while an irritant, classically, [[acts]] in a non-specific [[manner]].

It is a [[form]] of [[stress]], but conversely, if one is stressed by unrelated matters, mild imperfections can cause more irritation than usual: one is irritable; see also [[sensitivity]].

In more basic [[organisms]], assigning irritation the [[status]] of [[pain]] is the [[perception]] of the being [[stimulated]], which is not observable although it may be [[shared]] (see [http://en.wikipedia.org/wiki/Pain#Gate_control gate control theory of pain]).

It is not proven that oysters can [[feel]] [[pain]], but it is known that they [[react]] to irritation. When an irritating [[object]] becomes trapped within an oyster's shell, it deposits layers of calcium carbonate (CaCO3), slowly increasing in size and producing a [http://en.wikipedia.org/wiki/Pearl pearl]. This serves no reproductive [[purpose]] to the oyster, as pearls do not [[attract]] [[mates]] for the oyster. It is purely a [[defense]] [[mechanism]], to trap a potentially threatening irritant such as a [[parasite]] inside its shell, or an [[attack]] from outside, [[injuring]] the mantle tissue. The oyster creates a pearl sac to seal off the irritation.

It has also been [[observed]] that an [http://en.wikipedia.org/wiki/Amoeba amoeba] avoids being prodded with a pin, but there is not enough [[evidence]] to suggest how much it [[feels]] this. Irritation is apparently the only [[universal]] sense shared by even single-celled [[creatures]].

It is [[postulated]] that most such [[beings]] also [[feel]] [[pain]], but this is a [[projection]] – [[empathy]]. Some philosophers, notably [http://en.wikipedia.org/wiki/Ren%C3%A9_Descartes René Descartes], denied it entirely, even for such higher [[mammals]] as dogs or [http://en.wikipedia.org/wiki/Primate primates] like monkeys; Descartes considered [[intelligence]] a pre-requisite for the [[feeling]] of [[pain]].[http://en.wikipedia.org/wiki/Irritation]

[[Category: Biology]]