When a person is sick, and the illness is so severe that it's visible on their face, this emoji also impeccably expresses this condition. The face is unheroic or slightly red, the eyes are tired, and there's a thermometer in the mouth as if the body is burning with fever. This emoji is used when you're sick or want to convey that you're not feeling well and need to rest. The thermometer indicates the severity of the illness, and the pallor of the face reveals weakness.