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
"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
From Oil to Rash
The urushiol found in the sap of the poison ivy plant binds to skin cells
when it comes into contact, says Ziska.