In Hindu religion, married women have been applying sindoor in hair parting since ages. There are scientific reasons behind this belief. The parting line of a woman’s hair where sindoor is applied, there lies the most important spot, the spiritual center called Brahmarandhra, an aperture in the crown of head. This astral aperture is very sensitive, said to be the gateway to the absolute extending from perineum to the crown of the head, it is the place where parting is drawn and sindoor is applied.
Sindoor contains mercury, in it which is the only metal found in liquid form. When sindoor is applied in the hair-parting, mercury present in it, acts as a medicine because it is known for removing stress and strain and keeps the brain alert and active also.
The custom of filling sindoor in the hair parting is followed only after marriage because as soon as tying the nuptial knot, the free spirited girl suddenly gets transformed into a responsible wife and a daughter-in-law who has to take care of everybody present in her new home. Thus, under such responsibilities she sometimes get pressurized.
The mercury in the sindoor helps in cooling her down, bringing to her the mental peace .Hence sindoor having mercury in it works as a therapeutic medicine to deal with the pressures of new life by keeping the mind calm, composed and poised.