Scientists Say: Urushiol

This is the oil that gives poison ivy its itch

Leaves of three? Let it be! It’s the rhyme that warns people not to touch plants that contain urushiol, such as poison ivy. This oily compound can make your skin itch.

D. Gordon E. Robertson/Wikimedia Commons

By Bethany Brookshire

September 28, 2015 at 6:00 am

Urushiol (noun, “Yu-RU-shee-uhl”)

This is a natural oil made by certain plants, such as poison ivy, poison oak and poison sumac. Its contact with the skin can cause a nasty allergic reaction, with an itchy rash and blisters.

In a sentence

More carbon dioxide in the atmosphere might promote weeds such as poison ivy, and with it, more urushiol to make us itch.

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Power Words

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carbon dioxide A colorless, odorless gas produced by all animals when the oxygen they inhale reacts with the carbon-rich foods that they’ve eaten. Carbon dioxide also is released when organic matter (including fossil fuels like oil or gas) is burned. Carbon dioxide acts as a greenhouse gas, trapping heat in Earth’s atmosphere. Plants convert carbon dioxide into oxygen during photosynthesis, the process they use to make their own food.

urushiol A natural oil produced by plants belonging to the family Anacardiaceae, especially those in the Toxicodendron genus, such as poison ivy, poison oak and poison sumac. For most people, skin contact with this oil will lead to an allergic rash characterized by reddened skin and itchy blisters. The oil’s name comes from urushi, the Japanese term for lacquer.