Dermal Irritant Plants
These plants mainly act as irritants on skin contact, with resultant inflammation. Among the sensitising plants which induce plant dermatitis, the Compositae, the largest family of flowering plants are frequently found in homes and gardens. Severe eruptions are commonly associated with the highly sensitising plants of the genus Toxicodendron (Poison ivy, Poison oak, Poison sumac). Related species of Anacardiaceae (Lacquer tree, Ginkgo fruit tree, Marking nut tree, Cashew, and Mango) can also produce dermatitis. Some plants (Parsnip, Lime, Wild carrot) can cause photodermatitis, manifesting as erythema, blisters, or hypopig-mentation, on exposure to ultraviolet A light.
Table 10.3 lists a glossary of common skin lesions associ-ated with plant toxicity. Table 10.4 lists some plants that cause dermatitis.
· Topical corticosteroids—corticosteroid ointments with few or no additives are preferred. Optimal frequency of applica-tion is twice a day.
· For acute or weeping lesions, saline or aluminium subac-etate compresses can be applied 3 to 4 times a day to dry the skin.
· Itching can be relieved by oral antihistamines and lotions with menthol (0.25 to 0.5%).
· Oral corticosteroids may be required in addition to high-potency local applications for widespread eruptions (e.g. poison ivy dermatitis). Tapering the oral dose is necessary. Long-term local applications of corticosteroids must be avoided, since that may lead to atrophy, striae, purpura, folliculitis, and telengiectasiae.
· Prevention of irritant and allergic contact dermatitis may be attempted with barrier creams.
· Photosensitive reactions can be treated with antihistamines, topical antipruritic agents, topical corticosteroids, and compresses. Rarely, systemic corticosteroids may be required.