Apparatus and instruments for directing light energy to humans for medical and therapeutic purposes, namely, for treatment against infectious diseases caused by bacteria, viruses, parasites and fungi, improving immunity to infectious diseases caused by bacteria, viruses, parasites and fungi, treatment of neurological disorders and conditions, treatment of neurodegenerative diseases and traumatic brain injury, improving athletic performance, stimulation of the vagus nerve, and treatment of movement disorders where people have neurological disorders or conditions affecting the speed, quality and ease of body movements.