A mixture of nonvolatile hydrocarbons, derivatives of catechol with unsaturated C15 or C17 side chains, constituting the active allergen of the irritant oil of poison ivy, Toxicodendron radicans, poison oak, T. diversilobum, and the Asiatic laquer tree, T. verniciferum. [Jap. urushi, lac, + L. oleum, oil]
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uru·shi·ol (y)u̇-'rü-shē-.ȯl, -.ōl n a mixture of pyrocatechol derivatives with saturated or unsaturated side chains of 15 or 17 carbon atoms that is an oily toxic irritant principle present in poison ivy and some related plants of the genus Rhus
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uru·shi·ol (u-rooґshe-ol) a mixture of oleoresins found in the leaves and stems of various plants; it is one of the most common causes of allergic contact dermatitis (see urushiol dermatitis, under dermatitis). The most common urushiol-containing plants are in the family Anacardiaceae, such as in the genera Rhus (Toxicodendron), Anacardium, Mangifera, Schinus, and Semecarpus.Medical dictionary. 2011.