Irritant Contact Dermatitis

Plant substances that cause direct irritation to human skin nearly instantaneously, without a body-mediated reaction, are inducers of irritant contact dermatitis (ICD). These reactions can range in severity based upon season, a plant's age, weather, area and thickness of skin exposed, and geographic location. ICD can be caused by either a chemical substance released by the plant or by some physical feature that causes mechanical injury. The best example of the latter are cacti, while poinsettias are the most frequently seen example of the former. Cactus needles and other mechanically injurious plants are frequently associated with secondary infections, such as aseptic foreign body granulomas and chronic septic arthritis. Poinsettias (Euphorbia splendens) and related primarily tropical plants contain a milky white sap that can cause erythema and bullae. Another common irritant is calcium oxalate, which pierces the skin with small, needle-like crystals. ICD caused by calcium oxalate crystals has been noted in Mexico among workers in tequila distilleries and farmers on Agave tequilana plantations. The disease that results is known locally as "Mal de agaveros" (agave worker's sickness) and begins within 1 hour of contact with the agave plant (37-47).

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