Phytophotodermatitis on Thumb of a 28-Year-Old Woman

June 1, 2006

One week earlier, these asymptomatic linear brown streaks had appeared on the dorsal aspect of a 28-year-old woman's right thumb. When Ted Rosen, MD, of Houston questioned the patient about her recent activities, she said that she had just returned from a vacation in the Caribbean. During the trip, she had squeezed fresh limes into various beverages.

 

One week earlier, these asymptomatic linear brown streaks had appeared on the dorsal aspect of a 28-year-old woman's right thumb. When Ted Rosen, MD, of Houston questioned the patient about her recent activities, she said that she had just returned from a vacation in the Caribbean. During the trip, she had squeezed fresh limes into various beverages.

This lesion represents a classic example of phytophotodermatitis, a plant-related phototoxic reaction. An increased sun sensitization occurs because of skin contact with juice from the rind of limes (and, to a lesser extent, lemons). The sensitizing chemical--a psoralen--drips onto the skin and, after exposure to ultraviolet light (sunlight), the affected area may develop mild to severe erythema, blistering, or localized dyschromia. Localized dyschromia is essentially an accelerated tan.

No treatment is necessary. The pigmentation will gradually recede within 1 to 2 months.