close encounters with the environment

Botanical Briefs: Giant Hogweed— Heracleum mantegazzianum Sommier & Levier MAJ Thomas W. McGovern, MC, USA Theodore M. Barkley, PhD

Clinical Importance dren who use the hollow stems as a tel- Heracleum mantegazzianum causes phy- escope, pea-shooter, or whistle. tophotodermatitis that has been mis- taken for child abuse, as in a 13-month- Cutaneous Manifestations old girl with red finger marks on both Phototoxic reactions can occur from ul- shoulders. Her mother had cut down gi- traviolet A (UVA) exposure only 15 ant hogweed in her garden that day and minutes after contact with topical furo- subsequently laid her hands on her coumarins, but UVA sensitivity peaks 30 daughter.1 Those affected most often to 120 minutes after contact.2 Bizarre are sport fishermen, bathers, and chil- configurations of erythema, edema, and bullae appear after a latent period of The opinions and assertions contained herein roughly 24 hours. The inflammatory re- are those of the authors and are not to be considered as reflecting the views of the action peaks at 72 hours. These painful, Department of the Army or the Department of nonpruritic reactions are more often seen Defense. in middle to late summer when psoralen Dr. McGovern is in private practice in Grand concentrations are highest in the of- Rapids, Michigan. Dr. Barkley is with the fending plants and more skin is exposed Division of Biology, Kansas State University, Manhattan, Kansas. to direct sunlight. Wet skin, sweating, REPRINT REQUESTS to 4100 Lake Drive SE, and heat enhance the phototoxic re- Grand Rapids, Michigan 49546 (Dr. McGovern). sponse.3 To avoid misdiagnosis as poison ivy dermatitis, physicians must note that FIGURE 1. Heracleum the initial erythematous and bullous re- mantegazzianum growing action only occurs in sun-exposed areas. about 2 m tall in the Hyperpigmentation follows 1 to 2 weeks Denver Botanical after UVA exposure and lasts months to Gardens. Sunglasses years. Interestingly, areas affected by hanging from plant are for size comparison phototoxic reactions may remain hyper- (September 1995). sensitive to UVA light for years. Family The family names Umbelliferae and Apiaceae are both acceptable accord- ing to the International Code of Botan- ical Nomenclature.

Distribution This species is a native of the Caucasus and Kamschatka peninsula and has been

VOLUME 65, FEBRUARY 2000 71 GIANT HOGWEED

FIGURE 2. Giant compound umbel of Heracleum mantegazzianum approximately 60 cm across. Pedicels (small rays) arise from the end of each ray, and each pedicel supports a single flower of an umbellet. These are only visible in out-of-focus portions of the photograph (Denver Botanical Gardens, September 1995).

introduced into horticulture. Naturaliza- heads are made up of many small umbels tion and spread of the plant has occurred to make “compound umbels,” as seen in in central Europe, the United Kingdom, H. mantegazzianum (Figure 2). The fruits the United States, and Canada. are flattened, with a thickened central part and prominent thin wings on each Dermatitis-Inducing Plant Parts side; they have a distinctive parsley-like The black seeds, leaves, and roots con- odor when crushed. The flower heads are tain the most potent photosensitizers.4 sheathed at the base by one or more leaf- like bracts. Moreover, the leaves are large Nomenclature and deeply dissected, while the petioles As with most weedy plants, the taxon- are basally expanded and clasping the omy is complicated. Some botanists rec- stem. Close relatives of giant hogweed in- ognize several segregate species, but here clude carrots and parsley. we take a broad and inclusive view and recognize but a single variable species. Phototoxic Agents “Heracleum” probably derives from “Her- Because phytophotodermatitis is non- cules,” while “mantegazzianum” comes immunologic, it may be elicited in any- from Paolo Mantegazza, an Italian man- body given sufficient furocoumarins of-letters of the mid-19th century. and UVA. The plant contains 5- methoxypsoralen and 8-methoxypso- Identifying Features/Plant Facts ralen and acts as one of the main causes The plant was introduced to Kew Gar- of phytophotodermatitis in the United dens, England, for ornamental pur- Kingdom and United States. poses, but has now become a weed that is usually found in wet, shady sites. The Acknowledgment—Graphics assistance plant can grow nearly 4 m tall during from the Medical Photography Depart- its growing season and has large hollow ment, Wilford Hall Medical Center, stems (Figure 1). The giant umbels can Lackland Air Force Base, Texas. grow to 1 m in diameter (Figure 2). Cutting plants for the intended purpose REFERENCES of eradication may result in dispersal 1. Epstein WL: Plant-induced dermatitis. since the dried stems and flower heads Ann Emerg Med 16: 950-955, 1987. readily float downstream. 2. Kavli G, Volden G: Phytophotodermatitis. Members of the Umbelliferae are easy Photodermatol 1: 65-75, 1984. to recognize. Numerous small flowers are 3. Pathak MA: Phytophotodermatitis. Clin held in an “umbel” (a cluster of flowers Dermatol 4: 102-121, 1986. on stalks of roughly equal length arising 4. Lovell CR: Current topics in plant der- from a single point). Often, the flower matitis. Semin Dermatol 15: 113-121, 1996.

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