"I had my hand right on a bunch of poison oak."
Poison oak
Creative Commons AttributionPoison oak - Credit: Travis S.

Atlantic poison oak, a shrub native to the Southeastern United States, has gained its noli me tangere reputation from the oily sap that resides in the plant’s every part. Called urushiol, this substance triggers an allergic reaction upon skin contact, with symptoms including redness, swelling and irritation. Intensity and duration varies from person to person and may last from between five to 12 days, with severe cases sometimes running to 30.