Vibhuti-Sacred ash

Vibhuti is the sacred ash that many Hindus wear on their
forehead, head and chest.This is made in a Homam, where
special items like dried cowdung cakes, Samit twigs, ghee, etc
are offered to the fire with Vedic chants. The ash got after the
Homam is the sacred Vibhuti or Bhasmam. It is given as Prasadam
in Shaiva temples-Shiva means pure, and it is the purity of the mind
that is represented by the Vibhuti.

Devotees wear the Bhasma as "Tripundra" -3 lines of Vibhuti.

Significance:
Vibhuti, meaning "glory" is the ash that remains after
the offerings to the Vedic Yagna disappear. This reminds us of the
ultimate truth that one day, we will leave our mortal coils, our
possessions and desires, and only the Atma, the divine consciousness
is indestructable. By burning our desires, we attain supreme glory.
Bhasmam is an acronym made of 2 words-'Bhartsana', meaning
annihilation and 'Smaranam' meaning remembrance.
Thus, keeping in mind that we will be gone one day, we must
contribute for the well being of the world, without the "I"
feeling-for we'll be here only for some time, but the deeds we do
will be recorded in history.

Scientific Benefits:
Made of chemical compounds that are antimicrobial, the Vibhuti
can also be applied for certain skin problems-I have successfully
used this more than once, when certain plants/insects have given
me itching. It is hydrophilic and strongly absorbs moisture, thus
preventing colds and headaches. Also, in villages, when someone
gets drowned in a river/pond, people from surrounding houses
bring all the Vibhuti that they have and pour it on the rescued person.
The Vibhuti absorbs the water from even inside the body
and the person is saved.

Thus, the Vibhuti is not just a symbol to show off that you are a Hindu,
but has profound meaning contained in it.

Om Namah Shivaya!