Toxicodendron

Toxicodendron is a genus of flowering plants in the cashew family, Anacardiaceae. Its best-known species produce urushiol, an oil that can cause allergic contact dermatitis.

Anacardiaceae: A family of flowering plants that includes cashews, mangoes, pistachios, and Toxicodendron. Toxicodendron belongs to this family, whose members often contain irritant or allergenic compounds.
Poison ivy: Common name for several Toxicodendron species that cause urushiol-induced dermatitis. It is the best-known member of the genus in North America.
Type IV hypersensitivity: A delayed immune reaction driven mainly by sensitized T cells rather than antibodies. Urushiol-triggered dermatitis follows this immune mechanism and often appears after a delay.
Virginia creeper: A climbing vine in the grape family with five leaflets and no urushiol. Its five-leaflet leaves can be mistaken for poison ivy, but it does not cause urushiol dermatitis.
Urushiol: A mixture of oily organic compounds that causes allergic contact dermatitis in susceptible people. This resinous allergen is the main cause of reactions to many Toxicodendron species.
Poison oak: Common name for Toxicodendron species with oak-like leaflets that cause urushiol-induced dermatitis. It names a group of related species often confused with poison ivy.
Hapten: A small molecule that can provoke an immune response after binding to a larger carrier molecule. Urushiol acts as a hapten by binding skin proteins and creating immune targets.
Box elder: A maple species whose young leaves often have three leaflets. Its foliage can resemble poison ivy despite belonging to a different family.
Allergic contact dermatitis: An inflammatory skin reaction caused by an immune response to substances that contact the skin. Exposure to urushiol can trigger this delayed hypersensitivity reaction.
Poison sumac: A Toxicodendron species of wet habitats that can cause severe urushiol-induced dermatitis. It is a distinctive, less widespread source of exposure within the genus.

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