[L. irritatio]

1. A reaction to a noxious or unpleasant stimulus. It is important to distinguish between irritation and sensitization. A substance in contact with the skin may cause no irritation when initially applied but can cause allergic sensitization that will not become obvious until the material is applied again.
SEE: allergen; SEE: sensitization
2. An extreme reaction to pain or disease.
3. A normal response to stimulus of a nerve or muscle.

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