A much-cited study published in 2006 found that a rise in carbon dioxide both fueled the growth of the weed and increased the potency of urushiol, the oil at the root of the rash. Poison oak and poison sumac also contain urushiol, and all three can cause the blistering rash. Airborne sap-coated soot can also get into the eyes, nose, throat and respiratory system, according to the National Park Service.
That study involved planting PVC pipes into six plots of North Carolina’s 7,000-acre Duke Forest. Carbon dioxide was blown through holes in the pipes, which stretched to the tops of the tree canopies, while another control group of pipes vented normal air. Of all the plants, poison ivy was the hands-down winner, said Jacqueline Mohan, assistant professor at the University of Georgia and the study’s lead author.
“It was the most responsive species to the higher carbon dioxide in the atmosphere,” Mohan said. “The average little tree that I measured grew 8 percent faster. And poison ivy grew 149 percent faster than it would have under ambient, normal carbon dioxide conditions.”