Why Hindus used sandal paste,vibhuti or tilak on forehead

According to Hindu custom,  people are usually wearing sandalwood paste,  kumkum and Vibhuti on the forehead of men and women as the symbol of devotion to God.   But today using Vibhuti as a tradition to symbolize Hindu identity among Hindu religion.   Each Vibhuti has a different way to apply.   To honour Lord Shiva,  devotees are wearing Vibhuti across the forehead and other parts of the body in 3 horizontal lines called "Tripundra",  Vishnu devotees are wearing a sacred mark in the shape of "U" and Aghori's are wearing Tilak all over the body.   In ancient period,  people were in the control of Varna system in Hindu religion they were applied Tilak to represent their varna.   Brahmins wore chandan as a symbol of purity.   Kshatriyas applied red tilak on the forehead as the significance of their valour. Vaishyas wore yellow turmeric mark as prosperity and Sutras wore black tilak emphasising the service to all the above three varnas giving by Sutras.   As well as by wearing sandalwood paste scientifically people will get a cooling effect on the body while wearing Vibhuti indicates eternal death to becoming one with nature.   Not only wearing Vibhuti is the indication of worship to God but also there are some scientific facts behind while wearing tilak.   Hindu customs in most parts of India,  females are mostly wearing a sacred mark or Vibhuti on the forehead indicating the marital status of a woman.   Vedic Matters emphasising some scientific facts,   health benefits and spiritual beliefs while wearing these on the forehead.   Applying Vibhuti can bring glory and destroy evil is the spiritual belief behind wearing Vibhuti.   The health benefits of wearing sandalwood paste are reducing stress and relieving headache. The scientific fact using the middle finger to put on the sandalwood paste can allow magnetic waves to pass through.   Moreover, women are wearing red tilak emphasising Goddess Parvati and it increased the mental peace and physical energy of females.