The first variety is Toxicodendron vernicifluum, which grows in the regions of China, Japan, and Korea with the main component of "
urushiol." Second, Toxicodendron succedanea, which grows in Vietnam and Chinese Taiwan, has "laccol" as its main component.
The rash most of us get from poison ivy is caused by coming in contact with
urushiol, an oil found in the leaves, stems, flowers, berries, and roots of poison ivy.
These mostly include
urushiol, flavonoids, and phenols [3].
This form of contact dermatitis results from a type IV hypersensitivity reaction to
urushiol, a colorless oil in the leaves, stem, root, and fruit of poison ivy, poison oak, and poison sumac.
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.
All of this misery is thanks to a resinous oil, called
urushiol, found throughout the plant--in its leaves, stems, berries and roots, pretty much everywhere.
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.
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....
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. Once sensitized, your skin is likely to react to every subsequent exposure.