Me and My Mood mood rings are composed of several layers:
The lower layer is the base of the ring, usually silver or gold plated on brass. Brass is a more flexible material than silver or solid gold, which allows for the creation of jewelry with adjustable sizes.
A band of heat-sensitive liquid crystals is glued to the bottom of the base. A plastic or glass dome is placed on the liquid crystals. Like a magnifying glass, it will reveal the colors of the crystals.
Me and My Mood mood rings are sealed to prevent water or other liquids from seeping into the liquid crystals, as moisture will damage your jewelry irreversibly.
However, it is better to remove your jewelry before washing your hands, because if the water found a way to the crystals, they could freeze and stay forever black.