furocoumarin

Furocoumarins interfere with the skin’s ability to manage ultraviolet (UV) light exposure but are not themselves particularly harmful in moderate doses. However, if lime juice gets on your skin and you head out into the sun, the UV radiation activates the chemicals. Within hours—or sometimes…

…parts contain chemicals known as furocoumarins. Contact with the leaves and sap can cause phytophotodermatitis, in which the skin erupts in severe blisters if exposed to sunlight; blindness can occur if the sap enters the eyes.