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Climate Change Brings Super Poison Ivy

Researches Say Boost in Carbon Dioxide Has an Itchy Impact

From the WebMD Archives

Climate change isn't just increasing outdoor temperatures and warming up the oceans. It may also greatly increase your chances of getting a really bad case of poison ivy.

As the level of carbon dioxide in the atmosphere increases, it's boosting the growth of poison ivy plants, two recent studies show. These elevated carbon dioxide levels are creating bigger, stronger poison ivy plants that produce more urushiol, the oil that causes the allergic reaction and miserable poison ivy rash. The urushiol isn't just more plentiful; it might also be more potent.

"Initial data suggests that there may be a more [powerful] form of urushiol being produced with increasing carbon dioxide," says Lewis Ziska, PhD, a weed ecologist at the U.S. Department of Agriculture in Beltsville, Md., and a co-researcher of both studies.

In the last 50 years, Ziska says, the growth rate of the poison ivy plant has doubled. "The chances of encountering poison ivy and coming down with a rash are greater than they used to be," he tells WebMD.

About 80% of people are sensitive to the plant -- meaning they may develop a poison ivy rash if they come in contact with the plant. While the reaction is not typically serious, getting poison ivy can doom you to a week or more of miserable itching. The poison ivy rash can also raise your risk of getting a potentially serious skin infection from scratching your skin. Here's what you need to know before you head out to the woods, or the backyard.

Poison Ivy Studies

In Ziska's latest study, published in the July-August issue of Weed Science, his team compared the effects of four different concentrations of carbon dioxide on poison ivy plants, working in the laboratory. The carbon dioxide concentrations corresponded roughly to those that existed during the middle of the 20th century, the current concentration, and the concentration predicted for 2050 and 2090.

"What we found was even during that 50- or 60-year period that poison ivy could significantly respond to even a small change in carbon dioxide," Ziska says. The growth rate doubled, he says.

Ziska says his latest study confirms the findings of an experiment reported last year in the Proceedings of the National Academy of Sciences. In that study, Ziska and researchers from Duke University and other institutions compared poison ivy plants grown in ambient air with those grown in areas with a piped in system that increased the carbon dioxide levels. In the six-year study, the scientists showed that elevated carbon dioxide boosts the growth of poison ivy and results in the production of a more powerful form of the urushiol.