A 35-year-old woman comes to the clinic for an intensely pruritic rash on her wrists and forearms. Two days ago she spent the weekend clearing brush and vines from her backyard without gloves. The rash began within a day and has remained confined to areas that were directly exposed. Examination shows erythematous, edematous plaques with several linear streaks of vesicles and excoriations. She is afebrile and otherwise feels well. Which of the following is the most likely diagnosis?