"Bartender Burns" (Phytophotodermatitis)

We've already covered phytophotodermatitis and so I will not belabor the point, but the clue, primarily on the left hand, of hyperpigmentation in an irregular pattern with an accentuated border should cause you to prod the patient about exposure to citrus fruit and then sunlight, and the most common agent to cause this is Citrus latifolia, the Persian lime.  

Enough of you answered other citrus species that I gave credit for those answers as well.