When the term contact dermatitis of plant origin is employed, one immediately thinks of poison ivy and pictures an acute dermatitis venenata of sudden occurrence with marked swelling and vesiculation of the affected areas. This impression of plant dermatitis is due to the high incidence of acute dermatitis venenata occasioned by contact with the poison ivy vine or shrub, this plant being a violent skin irritant for a high percentage of those who touch its leaves or indirectly come in contact with some object contaminated with its sap. The few persons who are mildly sensitive to poison ivy react with only an erythematous eruption following such exposure. Occasional instances of a chronic type of dermatitis have been observed in such persons following frequently repeated contact with this plant.
Acute dermatitis occasionally follows contact with weeds, but the usual clinical picture is that of a chronic dermatitis. Sensitivity is usually moderate,
SHELMIRE B. CONTACT DERMATITIS FROM WEEDS: PATCH TESTING WITH THEIR OLEORESINSCHAIRMAN'S ADDRESS. JAMA. 1939;113(12):1085–1090. doi:10.1001/jama.1939.02800370001001