Delayed patch test reading after 5 days: The Mayo Clinic experience

Background Some patients may have delayed allergic patch test reactions that are not identified with a typical 5-day reading protocol. Objective To identify allergens with delayed-positive reactions and to determine whether a late reading (day 7-9) can be substituted for the day-5 reading. Methods We retrospectively reviewed medical records of patients who underwent patch testing for suspected allergic contact dermatitis from October 1997...