Irritation or exacerbation, 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 but mechanical, thermal and radiative stimuli can also cause irritation. Irritation also has non-clinical usages referring to bothersome physical or psychological pain or discomfort. In higher organisms, the allergic...
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