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 (o͝o-ro͞o′shē-ôl′, -ōl′, -ŏl′)
An oily, toxic substance composed of phenolic compounds that is present in the sap of various plants of the family Anacardiaceae and especially the genus Toxicodendron, including poison ivy, poison sumac, and the lacquer tree.

[Japanese urushi, lacquer + -ol.]


(ˈuːrʊʃɪˌɒl; uːˈruː-)
(Elements & Compounds) a poisonous pale yellow liquid occurring in poison ivy and the lacquer tree
[from Japanese urushi lacquer + -ol2]


(ʊˈru ʃiˌɔl, -ˌɒl)

a catechol derivative that is the irritant in poison ivy and its allies.
[1910–15; < Japanese urushi lacquer]
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References in periodicals archive ?
By the age of 8, most people are sensitized to urushiol.
Tecnu Original was the first product sold to remove urushiol, the rash-causing substance from poison ivy and oak plants, from skin.
All parts of the plant--vines, aerial roots, flowers, fruit and leaves--contain the irritating oil, urushiol.
Poison ivy produces urushiol as waterproofing, not for defense; humans, lucky as we are, are the only species "blessed" with sensitivity to the stuff.
Avoiding all contact with these plants is best; long pants, shirt sleeves, and gloves help avoid exposure, but this is often not practical for a child playing outside, and urushiol (the allergenic substance on the surface of these plants) adheres to clothes, and pets, and other things.
If you know your hands or arms touched the leaves, wash these areas as soon as possible with a skin cleanser, such as Tecnu, which is designed to remove the blister-causing urushiol oil that these plants produce.
It will form a protective barrier, making it more difficult for urushiol oil--which causes the poison ivy rash--to bond with skin.
Too late I learned that you can develop an allergic reaction to poison ivy after previously uneventful exposures, which induce a sensitivity to the plant's oily sap, urushiol.
Biological activity of urushiol and flavonoidsfrom Lac tree (Rhus verniciflua Stokes).
Poison ivy, poison oak, and poison sumac are plants that contain an irritating, oily sap called urushiol.
It is estimated that half the population is sensitized to the allergen, urushiol, and would have a reaction if they came into contact with any of these plants.
Trevino explained that these plants contain a resinous sap called urushiol that can cause a rash when it comes in contact with the skin in the estimated 50 percent of the population that is allergic to these plants.