Botanical Briefs: Phytophotodermatitis Caused by Giant Hogweed (Heracleum mantegazzianum)
Giant hogweed (Heracleum mantegazzianum) is an invasive flowering weed that can reach a height of 13 feet. Although it is the appearance of the plant that can draw attention, contact with the sap in combination with exposure to the sun can result in severe phytophotodermatitis. Due to the growing prevalence of giant hogweed, the number of cases of H mantegazzianum–associated phytophotodermatitis in the United States is increasing. We report the case of a 27-year-old man who presented with a blistering rash on the neck and arms that developed 18 to 24 hours after trimming giant hogweed plants without photoprotection. A diagnosis of giant hogweed phytophotodermatitis should be considered for patients presenting with acute erythema and bullae in sun-exposed areas after exposure to the plant. Additionally, the public would benefit from education, especially during summer months, on identifying the plant and reducing phototoxin exposure to reduce the risk for phytophotodermatitis.
PRACTICE POINTS
- The public should be educated, especially during summer months, about how to identify giant hogweed, reduce exposure to the plant’s phototoxin, and thus reduce the risk for severe phytophotodermatitis.
- Phytophotodermatitis should be included in the differential diagnosis when a patient presents with acute erythema and bullae in sun-exposed areas.
- Phytophotodermatitis can be treated by promptly washing the skin with soap and water, protecting the skin from exposure to UV light, and utilizing topical and oral steroids.
Further treatment might be required if bullous lesions are present. Small blisters can be punctured and drained; however, large blisters, extensive epidermal-dermal separation, and large areas of detached epidermis should simply be cleansed and dressed. An oral steroid also can be used to reduce inflammation in moderate and severe cases. Full-thickness injury might require surgical intervention.8
Clinical Case
A 27-year-old male landscaper presented to the emergency department with an increasingly painful blistering rash on the arms and neck of 1 day’s duration. He noticed bright red skin and blisters 18 to 24 hours after trimming what he identified as shoulder-high giant hogweed plants. Neither he nor his coworkers were wearing sunscreen or protective clothing as they cleared the plants for several hours. His coworkers developed similar rashes, but his rash was the most severe, requiring treatment in the emergency department.
Physical examination showed innumerable 2- to 10-mm, tense vesicles and bullae on a background of blanching erythema in a striking photodistribution along the neck (Figure 2) and arms (Figure 3). He had notable edema of both arms and several large 3- to 4-cm bullae on the ventral aspects of the forearms.
The patient was diagnosed with severe phytophotodermatitis secondary to contact with H mantegazzianum and was started on oral prednisone 70 mg daily (1 mg/kg/d), which was decreased by 10 mg every 3 days until the course of treatment was complete. He also was instructed to apply mupirocin ointment to open areas and petroleum jelly to intact skin. Additionally, he was advised to practice strict photoprotection for the near and distant future.
Within several days after treatment began, the phytophotodermatitis dramatically improved, with complete resolution in 1 week. Postinflammatory hyperpigmentation resolved after several weeks.
