Irritation

Irritation, in biology and physiology, is a state of inflammation or painful reaction to 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 (for example phenol and capsaicin) but mechanical, thermal (heat), and radiative stimuli (for example ultraviolet light or ionising radiations) can also be irritants. Irritation also has non-clinical usages referring to bothersome physical or psychological pain or discomfort.

Irritation can also be induced by some allergic response due to exposure of some allergens for example contact dermatitis, irritation of mucousal membranes and pruritus. Mucosal membrane is most common site of irritation because it contains secretory glands that release mucous which attracts the allergens due to its sticky nature.

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 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 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 (human).

In more basic organisms, the status of pain is the perception of the being stimulated, which is not observable although it may be shared (see gate control theory of pain).

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