Urushiol is an oily mixture of organic compounds with allergenic properties found in plants of the family Anacardiaceae, especially Toxicodendron spp. (e.g., poison oak, Chinese lacquer tree, poison ivy, poison sumac), Comocladia spp. (maidenplums), Metopium spp. (poisonwood), and also in parts of the mango tree as well as the fruit of the cashew tree. In most individuals, urushiol causes an allergic skin rash on contact, known as urushiol-induced contact dermatitis. The name urushiol is derived from the Japanese word for the lacquer tree, . The oxidation and polymerization of urushiol in the tree's sap in the presence of moisture allows it to form a hard lacquer, which is used to produce traditional Chinese, Korean and Japanese lacquerware. History Although urushiol-containing lacquers and their skin-irritating properties were well known in East Asia for several millennia, its first recorded Western texts were in 1624 by John Smith and he initially likened poison ivy to English Ivy. He did not classify it as a poison at first due to the speed with which its rash disappeared and Smith hypothesized that there may actually be medicinal uses for the plant. In the 18th and 19th centuries, many experiments were done in this area to determine whether or not this theory was true. Because that era's medicinal culture was dominated by plant-based treatments, physicians were hopeful that the strong effect this chemical produced on the body could be effective in some way. André-Ignace-Joseph Dufresnoy was one of the first to come up with a medicinal use for this chemical in 1780 when he boiled poison ivy to produce an infusion for internal use. This led to a distilled extract of poison ivy which he prescribed to many people suffering from skin problems and even paralysis. He claimed this treatment to have yielded several positive results. For many years, poison ivy was thought to fall into the Rhus genus; however, in the 1900s, it was reclassified into a more appropriate genus, Toxicodendron, meaning poison tree. There were many documented cases of irritations and allergic reactions from the plant, and its prevalence in medicinal use quickly dwindled. After this new categorization, scientists began attempts to determine what it was that rendered plants of this genus noxious, starting with a hypothesis of a volatile oil present in the plants. While this proved incorrect, Rikou Majima from Japan was able to determine that the chemical urushiol was the irritant.