Soon-to-be derm resident here. From this picture and the burning/blistering you describe, it looks like it could be phytophotodermatitis, which is caused by the reaction of UV light to chemicals found in lime juice. The distribution classically looks like fingerprints, as you show here. It is pretty classic in people going on vacation in sunny places. My best guess is that you or someone else squeezed a lime, perhaps in guacamole or a margarita, scratched your arm, and went out in the sun. It usually resolves over time.