The poison ivy ( Rhus toxicodendron ), poison sumach ( Rhus venenata ), and poison oak ( Rhus diversiloba of the Pacific Coast, U. S. A.) cause inflammation of the skin in certain persons who touch either one of these plants, or in some cases even if approaching within a short distance of them. The plants contain a poisonous oil, and the pollen blown from them by the wind may thus convey enough of this oil to poison susceptible individuals who are even at a considerable distance. Trouble begins within four to five hours, or in as many days after exposure to the plants.
