Rhus toxicodenron, commonly known as  the Poison Ivy grows in thickets and low grounds in North America, flowering in June. It was introduced into England as a plant in 1640. In 1798 Dufresnoy of Valenciennes first used it as a medicine. It was brought to his notice by the cure of a young man of an herpetic eruption  of six years’ duration, through his being accidentally poisoned with the plant.  Dufresnoy used it successfully in eruptive diseases, paralysis, rheumatism, and amaurosis. More than 200 years later, today it is very well known to be very useful specially in the wet weather.