The name says it all: poison ivy. Why in the world would you try to go near something with "poison" in its name? Perhaps because you thought it was something else. Poison ivy can resemble other harmless creeping vines. The plant produces an oil — urushiol — that's a known skin irritant. If you touch it, you can get a terrible, blistering rash that can last quite a while. Further, once you've been exposed, you can become allergic to it [source: WebMD].
At some point, someone thought that perhaps eating poison ivy would help people develop immunity to it. In 1987, a study was done on this — reported in the Archives of Dermatology — but the results came in negative. Eating poison ivy did not cause people to become immune to its nasty side effects. However, eating it will put you at risk for developing a severe irritation of your mouth, throat or your intestinal lining. Plus you can come down with everything from nausea and vomiting to fever and death [source: WebMD].