An earplug to be worn in the ear canal of a person has a thermochromic probe and stem portion that continuously monitors the core body temperature of the wearer and changes color reversibly upon detection of temperatures above or below a temperature range considered to be normal for tympanic temperature to visually indicate to the wearer or an observer that the wearer has an unsafe core body temperature. The earplug has an outer body formed of a soft resilient material configured to conform to the generally conical interior profile of the ear canal and become resiliently and removably engaged therein when pressed into the canal. The probe has a head portion and a radial flange configured to permit a desired insertion distance such that, when properly inserted, the head portion is near, but not in contact, with the tympanic membrane and engaged on the conical wall of the ear canal.
