Urushiol

Urushiol is a mixture of oily organic compounds found in plants such as poison ivy, poison oak, and poison sumac. It can trigger allergic contact dermatitis in susceptible people.

Allergic contact dermatitis: A delayed skin inflammation caused by an immune reaction to substances contacting the skin. Urushiol causes this skin reaction after sensitization.
Catechol: An aromatic compound with two hydroxyl groups on adjacent carbon atoms. Urushiol compounds share a catechol group that contributes to their reactivity.
Toxicodendron: A plant genus that includes poison ivy, poison oak, and poison sumac. Several species in this genus produce urushiol.
Urushiol-induced contact dermatitis: An itchy, often blistering skin eruption caused by immune sensitization to urushiol. This is the characteristic clinical outcome of urushiol exposure.
Allergic sensitization: An immune process that creates specific reactivity to an allergen after exposure. Whether exposure establishes sensitization helps determine later reactions to urushiol.
Type IV hypersensitivity: A delayed immune response driven chiefly by sensitized T cells rather than antibodies. This immune mechanism produces the rash after urushiol exposure.
Alkyl chain: A sequence of carbon and hydrogen atoms attached to a larger organic molecule. Urushiol compounds differ in the length and saturation of this attached chain.
Poison ivy: A Toxicodendron plant whose leaves, stems, and roots can contain urushiol. It is a familiar source of urushiol-induced dermatitis.
Poison ivy rash: An allergic skin eruption caused by contact with urushiol from poison ivy. It is a common named example of urushiol dermatitis.
Cross-reactivity: Immune recognition of similar molecular structures from different substances. Related plant compounds may provoke reactions in people sensitized to urushiol.

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