What oily resin causes Rhus dermatitis from plants in the Toxicodendron genus?
Answer
Urushiol
Rhus dermatitis, which encompasses reactions to poison ivy, poison oak, and poison sumac (all belonging to the Toxicodendron genus), is caused by direct contact with a specific substance contained within these plants. This substance is an oily resin known as urushiol. Urushiol is an extremely potent contact allergen, meaning exposure almost always results in an ACD reaction in sensitized people. A critical feature of urushiol is its persistence; it remains active on surfaces like tools or clothing for extended periods, which can lead to recurrent or delayed exposure long after the initial contact with the plant source.
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