Picture of Phytophotodermatitis With Blisters

Phytophotodermatitis is a rash occurring after contact between the skin and furanocoumarins, a class of chemicals found in many plants. The active substance within the furanocoumarins is psoralen, which reacts with UVA light to cause an intense cutaneous reaction. Phytophotodermatitis does not involve any immune mechanism but must be differentiated from an allergic response. Rash characteristics can range from simple hyperpigmentation to erythema, vesicles, or bullae.