I am now living in Northeastern Brazil and am just beginning to learn about plants here- very different than U. S. plnats in some ways. I had a bad experience yesterday with a pencil plant cactus-picked up someone's discard on the side of the road and got milky sap on my arm. Later that evening, started having lips tingle and numb, then tongue swollen, then roof of mouth began to numb. I took benedryl until got relief, arm had hives this am. Never knew how poisonous this plant was- admired it in U.S. just didn't own any. I was fortunate enough to have researched plant on web last night and recognized symptoms as they began, likely saved trip to a hospital is Brazil.