[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; sensitization.

2. An extreme reaction to pain or disease.
3. A normal response to stimulus of a nerve or muscle.

sympathetic i.The response of an organ to irritation in another organ.