Sap and Sun: A Case of Phytophotodermatitis.

We report a case of phytophotodermatitis caused by cow parsnip (Heracleum maximum) exposure affecting a hiker in Colorado. Phytophotodermatitis is a phototoxic skin reaction to UV-A rays after contact with photosensitizing plant substances that presents as a burning, painful rash, often with blisters. Treatment is supportive, including wound hygiene, analgesia, and anti-inflammatories. Avoiding offending plants, protecting the skin from sun, and immediate washing with soap and water after plant contact are the primary means of prevention. We have included a table and photos of plants found in the United States that can cause phytophotodermatitis. Medical providers should include phytophotodermatitis in the differential diagnosis of blistering rashes in patients who have been outdoors with possible exposure to offending plants.