Disclosed is an illuminating device that includes a light source and a mouthpiece. The mouthpiece is configured to adapt the light source thereon and is capable of being accommodated within a user's mouth. The mouthpiece includes a switch and a power source. The switch is electrically connected to the light source. The power source is electrically connected to the switch and the light source and is capable of providing electrical power to the light source for illumination. Upon receipt of the mouthpiece within the user's mouth and application of pressure on the switch by the user's teeth, the light source is illuminated.