You can’t catch poison ivy from someone with a poison ivy rash unless they still have the oil from the plant on their skin. The oil, which is called urushiol, is the toxin that causes the rash. “The rash is not contagious, and that’s the key,” Adesman says.
If you do get the oil on your skin, wash it off as quickly as possible with lots of water. Some experts also suggest washing with a product like Technu.