Phytophotodermatitis

The parents of a 6-year-old girl were concerned about the hyperpigmentation of their child’s fingers. Two weeks earlier, lime juice was accidentally spilled on the patient’s fingers during a barbecue on a sunny beach. By the following morning, the affected digits had turned red. A few days later, the erythematous areas became hyperpigmented. Phytophotodermatitis was diagnosed by Drs Alexander K. C. Leung and Justine H. S. Fong of Calgary, Alberta. The family was reassured of the benign nature of the condition. When the child was seen 4 months later, the hyperpigmentation had disappeared. Phytophotodermatitis results from the interaction of solar radiation and photosensitizing compounds, such as furocoumarins (psoralens) in various plants. After the psoralens are exposed to UV-A radiation, they form phototoxic compounds that cause direct damage to the DNA of epidermal cells. This damage induces cutaneous eruptions, which range from erythema to hyperpigmentation and, less commonly, vesicles and bullae. The lesions usually appear a few hours to a few days after exposure to the sun. The plants that most commonly cause phytophotodermatitis are limes, lemons, and celery; oranges, garlic, hot peppers, and parsley also contain furocoumarins. No treatment is necessary for this benign condition. The hyperpigmentation usually fades over time.