Washington ? 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 report Monday.

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’s considered a major contributor to global warming. Greenhouse gases have been steadily increasing in the atmosphere since the Industrial Revolution.

Poison ivy is common in woods across the country, making it a bane of hikers, campers, fighters of forest fires and even backyard gardeners.