Why Hindu Married Women wear Sindoor (Vermillion) on her forehead, by parting their hair.
Source: Big Indian Wedding
In Hinduism, wearing Sindoor or vermilion holds lot of importance and traveled through more than 5,000 years of Hindu culture. Wearing Sindoor (Vermillion) is the symbol of married women. As per Hindu religion only Hindu married women wear Sindoor (Vermillion) between the hairs by parting their hair. Bachelor women or widow are restricted and can’t wear vermillion as per Hindu religion.
It is a visible expression of the desire of Indian women for their husbands’ (Suhag) longevity. Traditionally therefore, widows did not wear Sindoor. Apart from women’s married symbol wearing Sindoor (Vermillion) beauty of her face also gets enhanced.
In other words, women look awesome and beautiful after wearing vermillion (Sindoor) on their forehead, between the hairs, in the parting of hairline. When the marriage ceremony is held the bridegroom himself adorns her vermillion (Sindoor) 5/7 times by pinching (Chutki) on the forehead, between the hairs, in the parting of hairline of women by the chanting of mantras by priest and after sindoor dana, marriage of the women completes. The women after her marriage wear everyday Sindoor (Vermillion) on her forehead, between the hairs, in the parting of hairline and pray for long life of their husband from God. Flashing of Sindoor between the hairs, in the parting of hairline of women is the most important and vital part of her beautification (Shringaar) and a scientific, cultural and religious reasoning is also behind wearing Sindoor (Vermillion) by the women.
If we read Hindu astrology, Mesha Rashi, the House of Aries is located on the forehead of the human body and Mars is the Lord of Mesha Rashi. Since we know the colour of Mars is red, it is believed to be very auspicious color (signs of saubhagya (good fortune) meant for longevity and this is the reasoning that the married women wear red color sindoor (vermillion) between the hairs at the forehead, the parting of the hair. In Hindu Shastras and as per Hindu mythology, it is mentioned that Sindoor is the symbol of the female energy of Parvati and Sati and symbolizing marital status of the women.
Mythological Scholars / Pundits describes red color is the color of power and vermillion symbolizes female energy of Parvati or sati. Legends of Hindu Mythology also describes that Sati, wife of Lord Shiva was the ideal wife who gave her life for the honor of her husband by burning herself in Agnikund. Since then it is believed that every married Hindu women emulating Sati and it is also believed that Goddess Parvati, wife of Lord Shiva protects all those men (Husbands) whose wives adorning (Applying in their Maang) Sindoor (Vermillion) to their parting of hair.
Also interesting to note here that there is a physiological significance too of wearing Sindoor (Vermillion) by married women and that is because Sindoor (vermillion) is a mixture of turmeric-lime and the metal mercury and because of its intrinsic properties, mercury, besides control blood pressure