urushiol

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urushiol

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July 14, 2026

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Why does poison ivy make people so itchy? — Why does poison ivy make people so itchy? Learn how the oil urushiol, secreted by poison ivy (Toxicodendron radicans), causes allergic reactions and how those reactions can be treated.

Urushiol is an oily, toxic irritant substance found in poison ivy, poison oak, and poison sumac. This substance is present in nearly all parts of the poison ivy plant. When urushiol comes into contact with skin, it can cause a severe, itchy, and painful inflammation known as contact dermatitis.123

The urushiol oil can remain on clothing, tools, or soil for up to a year, leading to poisoning even if a person doesn't directly touch the plant. This reaction is a type of delayed hypersensitivity, where the immune system becomes sensitized to the chemical after initial exposure.243

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immune system disorder
Contact hypersensitivity and dermatitis
It secretes an oil called urushiol, which is also produced by poison oak (T. diversilobum), the poison primrose (Primula obconica), and the lacquer tree (T. vernicifluum). When urushiol comes in contact with the skin, it initiates the contact hypersensitivity reaction.
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It secretes an oil called urushiol, which is also produced by poison oak (T. diversilobum), the poison primrose (Primula obconica), and the lacquer tree (T. vernicifluum). When urushiol comes in contact with the skin, it initiates the contact hypersensitivity reaction.
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lacquer
…of the lacquer tree is urushiol (from urushi, the Japanese word for lacquer), a substance that can cause contact dermatitis if the lacquer touches the skin before it has cured. The cured lacquer produces a hard, glossy coating that is highly prized in traditional decorative arts. See also lacquerwork.
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…of the lacquer tree is urushiol (from urushi, the Japanese word for lacquer), a substance that can cause contact dermatitis if the lacquer touches the skin before it has cured. The cured lacquer produces a hard, glossy coating that is highly prized in traditional decorative arts. See also lacquerwork.
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poison ivy
The toxic principle, urushiol, is produced in the resinous juice of the resin ducts of the leaves, flowers, fruits, and bark of stems and roots but not in the pollen grains. Being almost nonvolatile, the urushiol may be carried from the plant on clothing, shoes, tools, or soil…
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The toxic principle, urushiol, is produced in the resinous juice of the resin ducts of the leaves, flowers, fruits, and bark of stems and roots but not in the pollen grains. Being almost nonvolatile, the urushiol may be carried from the plant on clothing, shoes, tools, or soil…
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poison oak
These species contain urushiol, and contact with the leaves and sap can cause a severe, itchy, and painful inflammation of the skin. Like many other lobe-leafed plants commonly called “oak,” neither species of poison oak is a true oak of the genus Quercus.
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These species contain urushiol, and contact with the leaves and sap can cause a severe, itchy, and painful inflammation of the skin. Like many other lobe-leafed plants commonly called “oak,” neither species of poison oak is a true oak of the genus Quercus.
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poison sumac
…on exposure to air, contains urushiol and is extremely irritating to the skin for many people. The plant is considered more allergenic than the closely related poison ivy (Toxicodendron radicans) or western poison oak (T. diversilobum). The itchy and painful inflammation, known as contact dermatitis, can persist for days or…
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…on exposure to air, contains urushiol and is extremely irritating to the skin for many people. The plant is considered more allergenic than the closely related poison ivy (Toxicodendron radicans) or western poison oak (T. diversilobum). The itchy and painful inflammation, known as contact dermatitis, can persist for days or…
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