CBS: Poison ivy, poison oak and poison sumac plants are becoming larger and stronger, a trend that's been developing over recent years, according to researchers. That may be a combination of the plant's nature to cause more severe reactions over time and the increased carbon dioxide in the atmosphere as a result of global warming.
A substance in the plants called urushiol oil is to blame for the notorious itchy rash that develops in people who touch it. According to the U.S. Forest Service, 70 to 85...