Vibhuti:(Sanskrit) "Resplendent, powerful." Holy ash, prepared by burning the dried cow dung in an airtight oven along with other substances and processed through a series of rituals only then it accepted as holy ash. We can call it in simple word as be "ashes of cow-dung". It symbolizes purity and is one of the main sacraments given at puja in all occasions. Vibhuti symbolizing the burning of one's negative qualities.
Is the fourth Avarana and smearing it on the body is the fourth religious exercise. All ritualistic exercises serve the twofold purpose of increasing the love for God and adherence to the religious life.
Vibhuti and Bhasma are synonyms. Vibhuti has several symbolic meanings. Placed on the forehead of devotees with three stripes, it covers the mark of the spiritual Guru , Linga and Jangama that sees development of mystic insight as the primary path to Self-realization
The wearing of Vibhuti or Bhasma reminds us of the pure white form of GOD. It also denotes the ultimate state of everything when it is completely burnt.
Those who wear such Vibhuti are unequalled in all respects in this world. Such Vibhuti, which is Reality,the thought-free and wonderful wisdom (Jnana), is eternal divine wealth.
Vibhuti contains antibiotic properties and cures few of the skin diseases.
 From the book "Vachana", pub: Basava Samiti Bangalore 2012.