FINDINGS: Poison Ivy Thrives as Planet Warms Tuesday, May 30, 2006; Page A05; Washington Post Another reason to worry about global warming: more and itchier poison ivy. The noxious vine grows faster and bigger as carbon dioxide levels in the atmosphere rise, researchers reported yesterday. And a CO2-driven vine also produces more of its rash-causing chemical, urushiol, conclude experiments conducted in a forest at Duke University where scientists increased carbon-dioxide levels to those expected in 2050. Carbon dioxide is a greenhouse gas — a chemical that traps heat similar to the way a greenhouse does — that is considered a major contributor to global warming. Poison ivy’s itchy, sometimes blistering rash is one of the most widely reported ailments, with more than 350,000 reported cases a year. Compared with poison ivy grown in usual atmospheric conditions, those exposed to the extra-high carbon dioxide grew about three times larger — and produced more allergenic form of urushiol, scientists from Duke and Harvard University reported. Their study appears in this week’s Proceedings of the National Academy of Sciences.