Mental Floss

A Few Quick Poison Ivy Facts

Kara Kovalchik
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Summer is winding down, but a lot of us are still venturing through the local flora and fauna bare-legged. As a public service, we thought we'd scratch up some poison ivy facts.

"¢ Poison ivy can be found in every U.S. state except for California, Alaska and Hawaii (California has plenty of poison oak, however) and in every Canadian province apart from Newfoundland and Labrador. Researchers at Duke University have found that higher concentrations of carbon dioxide in the atmosphere not only cause poison ivy to thrive, but also increases the intensity of urushiol. As a result, poison ivy is no longer restricted to the most remote hiking trails; it can be found in public parks, through the cracks in urban sidewalks and in backyard gardens.

"¢ Urushiol is the active ingredient in poison ivy (and poison oak) that gives some folks an itchy rash.

Notice we said "some" folks "“ truth be told, not everyone who comes in contact with an offending plant will break out in a rash. About one in five humans will have no reaction whatsoever when exposed to the sticky sap emitted from these plants. The remaining 80 percent will break out in an itchy, blistery rash from contact either direct (from the plant itself) or indirect (say, from petting a dog that has urushiol in its fur). Resin from poison ivy has a long half-life and people have been known to get a rash simply by touching a gardening tool or pants leg that had made contact with the plant more than a year prior.

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"¢ Hopefully the Obama family is being mindful of the vegetation while they vacation on Martha's Vineyard. Poison ivy flourishes on the island as a shrub and a climbing vine, as well as ground cover. Nearby pharmacies do booming business selling Technu, a non-prescription cleanser that removes urushiol from the skin. Horticulturist Polly Hill, who founded the island's public arboretum, used to eat poison ivy leaves as a child in an effort to build up an immunity to its effects. And, for what it's worth, Ms. Hill lived to the ripe age of 100 without ever suffering a poison ivy rash.

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