Middle East DVEP - Armed Forces Pest Management Board

C. Medical Botany.1. Plants that Cause Contact Dermatitis.Plant dermatitis is a problem of enormous magnitude. Plants produce many clinicalclasses of contact dermal injury. These include mechanical injury, delayed contactsensitivity, contact urticaria, phototoxicity and photoallergy, primary chemical irritation,or some combination of these. Plants causing contact dermatitis in the Middle East arelisted in Table 3.Mechanical injury by splinters, thorns, spines, and sharp leaf edges can produce visualimpairment or fungal and bacterial infections at the site of injury.Members of the Rhus group (poison ivy, oak, and sumac) are the most frequent causes ofacute allergic contact dermatitis. A large portion of the US population is sensitive tourushiol in the sap of these plants. Sensitivity to a substance develops after initialcutaneous contact. Once sensitized, subsequent exposure will elicit an allergic response inwhich the whole body surface becomes reactive. Even smoke from burning plants canproduce an allergic response. Barrier creams have been developed to prevent contactdermatitis in people sensitive to urushiol.Contact urticaria may result from immunological or nonimmunological host responses,although the latter is more common. Nettles, such as Urtica spp., are examples of plantsthat cause nonimmunologic contact urticaria. These plants have hollow stinging hairs thatinject a chemical after penetration of the skin. A burning sensation and pruritis occuralmost immediately.A number of cultivated plants of the carrot and rue families sensitize the skin to longwaveultraviolet light. Within 6 to 24 hours of contact with the plant and exposure tosunlight or fluorescent light, the area of contact will selectively burn. In some cases,hyperpigmentation may persist for several months.Some plants contain primary chemical irritants that produce skin damage resembling thatfrom contact with a corrosive acid. The reaction depends on the potency of the irritant.The most serious reactions involve the eye. Daphne spp. and Euphorbia spp. areexamples of plants containing chemical irritants.For addition information on plants causing dermatitis, contact the Armed Forces MedicalIntelligence Center, Fort Detrick, MD. (301) 619-7574, DSN: 343-7574; FAX: (301) 619-2409 (DSN = 343).146