Shikha is a tuft of hair at the back of head specifically kept by Vaishnavas and Brahmanas. According to the Vedic culture, when a person undergoes the Cuda-Karana-samskara (hair-cutting ceremony) and upanayana (Vedic initiation), he must shave his head, leaving a tuft of hair called a sikha.
Our human body has seven energy centers, or chakras, starting from the first at the base of the spine (Mooladhara Chakra) to the seventh and last one – the Sahasrara Chakra. The kundalini is the snake-like subtle energy lying coiled at the base chakra, which through yogic exercise can be made to uncoil and rise up through the chakras, finally to the top one, the Sahasrara. The master, one who has achieved the final goal, or enlightenment or perfection or union, is one wherein the kundalini would have reached the Sahasrara chakra.
The Shika covers that part of the skull wherein the final chakra – the Shasrara Chakra lies. He retains the hair to protect it.
Scientific Reasons for Having a Shikha:
(A) A person who keeps Shikha attracts cosmic energy which imparts enlightenment.
(B) The small portion of hair that hangs from behind our head applies little pressure on our brains that helps one to improve concentration and mind control and improve memory.
From the time of the Vedas, the Shikha was a distinguishing feature of the Brahmins, Kshatriyas, and Vaishyas. It signified the ‘twice-born’ or all those Upanayanam has been performed. At the time of Chudakarana, a tuft of hair was left on the head, never to be cut. This Shikha covered a large part of the brain. According to Sushruta, the reason that a few tufts are left on the head is that at the crown, an artery joins a critical nerve juncture. Since an injury to this part of the head is believed to be fatal, it was considered necessary to protect the area by keeping a tuft of hair over it. The Shikha was a symbol of superiority and of cleanliness.
Any religious or auspicious ceremony required the Shikha to be tied in a knot. The knot was tied to the accompaniment of the Gayatri Mantra. An untied Shikha was a symbol of disgrace, impurity, and mourning.