Kumkuma is most often applied by Indians to the forehead. The reason for this particular location has to do with the ancient Indian belief that "the human body is divided into seven vortices of energy, called chakras, beginning at the base of the spine and ending at the top of the head. The sixth chakra, also known as the third eye, is centered in the forehead directly between the eyebrows and is believed to be the channel through which humankind opens spiritually to the Divine". Thus the kumkuma is placed at the location of the body which is believed by Indians to be the most holy.
German: Indisch - Roter Punkt auf der Stirn
1. Huyler, Steven. "The Experience: Approaching God". In The Life of Indians , ed. Vasudha Narayanan and John Stratton Hawley. Los Angeles: University of California Press, 2006.