The student was allergic to cashew nuts, according to the Corriere della Sera, and went into anaphylactic shock after eating the sandwich in the Casilino area of the Italian capital.
She had already felt ill in the restaurant and rushed back to her student accommodation on nearby Via Casilina where she collapsed unconscious, the Corriere reports.
Her fellow American students rushed to her aid by administering cortisone, however despite this and the repeated efforts of paramedics, the young woman died at the scene.
An investigation is underway into the tragic incident, which may have occurred due to a language barrier between the student and restaurant staff.
Last October a 14-year-old British girl with a peanut allergy died of anaphylactic shock after dining in a pizzeria in Rome.