A sheep in wolf's clothing?

A 25-year-old college student with no medical history sought care at our hospital for a nonproductive cough, subjective fevers, myalgia, and malaise that he'd developed 10 days earlier. The day before his visit, he'd also developed scratchy red eyes and a sore throat. He said he'd taken an over-the-counter cough suppressant to help with the cough, but his eyes and lips developed further redness and irritation. On examination, the patient demonstrated conjunctival suffusion, periorbital edema, diffuse oral stomatitis with pseudomembranous crusting, and nasal crusting. His vital signs were within normal limits, and he had no epithelial skin eruptions or erosions in any other mucosal regions. What's your diagnosis?