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.

The skin of the hands becomes red, swollen, painful, and itching. Soon little blisters form, and scratching breaks them open so that the parts are moist and then become covered with crusts. The poison is conveyed by the hands to the face and, in men, to the sexual organs, so that these parts soon partake of the same trouble. The face and head may become so swollen that the patient is almost unrecognizable. There is a common belief that ivy poison recurs at about the same time each year, but this is not so except in case of new exposures. Different eruptions on the same parts often follow ivy poisoning, however.

Treatment. A thorough washing with soap, especially green soap, will remove much of the poison and after effects. Saleratus or baking soda (a heaping tablespoonful of either to the pint of cold water) may be used to relieve the itching, but ordinary “lead and opium wash” is the best household remedy. Forty minims of laudanum[9] and four grains of sugar of lead dissolved in a pint of water form the wash. The affected parts should be kept continually wet with it. Aristol in powder, thoroughly rubbed in, is almost a specific.