Giant Hogweed burns

A 13-year-old boy presented to A&E with an erythematous rash on his lower legs, arms and torso after swimming in a local river the previous day. On initial examination, he appeared well and afebrile with several irregularly shaped erythematous lesions that were tender and warm to touch (figure 1A,B). Inflammatory and infection markers were normal but intravenous flucloxacillin was commenced for possible cellulitis. The following day the lesions progressed into a distressing painful blistering rash. The diagnosis remained unclear until the boy’s father visited and proclaimed the lesions Giant Hogweed burns. Diagnosis was confirmed by internet searches and collab-oration with dermatology. Treatment of Hogweed-induced phytophotodermatitis follows that for chemical burns. Large bullous lesions were de-roofed and potassium permanganate impregnated dressings used for their bactericidal and astringent properties. The addition of par-affin gauze dressings showed an immediate improvement in pain and prevented further damage from ultraviolet (UV) radiation. Oral and topical steroids were used to reduce inflammation and flucloxacillin continued to manage secondary infection. Giant Hogweed or Heracleum mantegazzianum (figure 2) is commonly found at the water’s edge. Reaching up to 4 m in height, their sap contains toxic chemicals known as linear fura-nocoumarins.1 On contact with skin, they produce a phytopho-todermatitis.2 This cutaneous phototoxic inflammatory eruption results from contact with light-sensitising psoralens and long-wave UV radiation.2 Activated psoralens bind to RNA and nuclear DNA leading to cell membrane damage and oedema.3 Postinflammatory hyperpigmentation lasting months may ensue followed by photosensitivity that requires UV-A blocking sunscreens.