The mark on forehead invokes a feeling of sanctity in the wearer and others. It is recognized as a religious mark. Its form and colour vary according to one’s caste, religious sect or the form of the Lord worshipped.
In earlier times, the four castes (based on varna or colour) - Brahmana, Kshatriya, Vaishya and Sudra - applied marks differently. The brahmin applied a white chandan mark signifying purity, as his profession was of a priestly or academic nature. The kshatriya applied a red kumkum mark signifying valour as he belonged to warrior races. The vaishya wore a yellow kesar or turmeric mark signifying prosperity as he was a businessman or trader devoted to creation of wealth. The sudra applied a black bhasma, kasturi or charcoal mark signifying service as he supported the work of the other three divisions. Also Vishnu worshippers apply a chandan mark on forehead of the shape of "U,” Shiva worshippers applied holy ash in the form three horizontal lines, Devi worshippers a red dot of kumkum and so on. The mark on forehead cover the spot between the eyebrows, which is the seat of memory and thinking. It is known as the Aajna Chakra in the language of Yoga.
The mark on forehead is applied with the prayer - "May I remember the Lord. May this pious feeling pervade all my activities. May I be righteous in my deeds.” Even when we temporarily forget this prayerful attitude the mark on another reminds us of our resolve.
The mark on forehead is thus a blessing of the Lord and a protection against wrong tendencies and forces. The entire body emanates energy in the form of electromagnetic waves - the forehead and the subtle spot between the eyebrows especially so. That is why worry generates heat and causes a headache. The mark on forehead cools the forehead, protects us and prevents energy loss. Sometimes the entire forehead is covered with chandan or bhasma. Using plastic reusable "stick bindis" is not very beneficial, even though it serves the purpose of decoration.
Of all the marks, bhasma or holy ash is something special. But why?
The ash of any burnt object is not regarded as holy ash. Bhasma (the holy ash) is the ash from the Yagna(sacrificial fire) where special wood along with ghee and other herbs is offered as worship of the Lord. Or the deity is worshipped by pouring ash as abhisheka and is then distributed as bhasma.
Bhasma is generally applied on the forehead. Some apply it on certain parts of the body like the upper arms, chest etc. Some ascetics rub it all over the body. Many consume a pinch of it each time they receive it.
The word bhasma means, "that by which our sins are destroyed and the Lord is remembered.” Bha implied bhartsanam ("to destroy") and sma implies smaranam ("to remember"). The application of bhasma therefore signifies destruction of the evil and remembrance of the divine. Bhasma is called vibhuti (which means "glory") as it gives glory to one who applies it and raksha (which means a source of protection) as it protects the wearer from ill health and evil, by purifying him or her.
Yagna (offering of oblations into the fire with sacred chants) signifies the offering or surrender of the ego and egocentric desires into the flame of knowledge or a noble and selfless cause. The consequent ash signifies the purity of the mind, which results from such actions.
Also the fire of knowledge burns the oblation and wood signifying ignorance and inertia respectively. The ash we apply indicates that we should burn false identification with the body and become free of the limitations of birth and death. This is not to be misconstrued as a morose reminder of death but as a powerful pointer towards the fact that time and tide wait for none.
Bhasma is specially associated with Lord Shiva who applies it all over His body. Shiva devotes apply bhasma as a tripundra. When applied with a red spot at the center, the mark symbolizes Shiva-Shakti (the unity of energy and matter that creates the entire seen and unseen universe).
Urvaa rukamiva bhandhanaan
Mrytyor muksheeyamaa amrutaat
"We worship the three-eyed Lord Shiva who nourishes and spread fragrance in our lives. May He free us from the shackles of sorrow, change and death – effortlessly, like the fall of a rip brinjal from its stem."
It has immense health benefits also as per Ayurvedic terms if it is a real bhasma obtained from yagna, where Gold, ornaments and many herbs are incinerated.