Poison ivy produces an oily sap called urushiol throughout the plant. Exposure to that oil causes an allergic reaction in about 85% of people. Urushiol is extremely durable and can remain on clothing, fur, or tools for long periods after initial exposure. If you’re exposed to it, wash thoroughly with cool water and a degreasing soap, then use rubbing alcohol and scrub under the fingernails with a brush, and wash all the exposed clothing. Poison ivy can also be extremely toxic if inhaled, so the plant should never be burned.

> See if you know how to recognize poison ivy. (More, w/quiz) 
> Urushiol can remain allergenic on clothing for up to five years—or longer. (More)

When urushiol comes into contact with our skin, it binds to skin proteins, ultimately triggering an immune system response as if the body’s under attack. The resulting inflammatory response leads to the rash and other uncomfortable symptoms.

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> Poison ivy was sent to Europe in the 1600s as an exotic, ornamental oddity. (More)

> Experiments in the 1990s simulated potential 2050 conditions—learn how poison ivy fared. (More)