Poison Ivy

Poison ivy's characteristic rash is caused by an allergic response to an oily compound in the plant called urushiol.

During the French Revolution, a botanist's letter asking about "dear Rhus" (poison ivy) was intercepted and led to authorities' suspicions he was conspiring with the Russians.

Poison ivy's rash-causing compound is found in the plant's roots, stem, and leaves—so coming into contact with any part of the plant can lead to rashes for the 85% of people who are allergic to it.

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

Poison ivy is in the same family as mangoes, cashews, and pistachios—and they all produce oily urushiol in their raw unprocessed state, and chewing mango skin can produce blister rashes.

Poison ivy is projected to be larger and more resilient due to climate change

Between 10 million and 50 million people in the US develop rashes from poison ivy, poison sumac, and poison oak annually.

Urushiol, the oily toxin in poison ivy, can remain allergenic on clothing for years.

Poison ivy, which produces urushiol throughout the plant, not just in the leaves, can cause year-round rashes.

Scientists testing how climate change affected plants found in a years-long simulation study that poison ivy grew 70% faster than it did without extra carbon dioxide.