(from Homa Therapy Teacher Certification information)
Vedic knowledge states that a purified energy field is created around Homa fires. This energy field can be influenced by the energy fields of people who are near the fire. To preserve the purity of this subtle energy field of the Agnihotra fire, we don’t perform Agnihotra (or other Homa fires) and don’t come close to it when our own energy field is disturbed – as in the case of high fever or some bleeding.
If we cut ourselves, we stay away for as long as blood is flowing. With Agnihotra ash (and/or turmeric) we can usually stop the bleeding quickly so that we are again able to perform Homa fires.
For energetic reasons, the same discipline is followed by women during their monthly cycle. During menstruation, women are surrounded by an energy that travels downward in a spiral shape towards the earth. Agnihotra creates an energy which flows upwards towards the atmosphere, also in spiral form. Both are cleansing energies and both are important, but they work in different ways and, to an extent, they nullify each other. Therefore, as long as there is bleeding, women should refrain from performing Agnihotra or other Homas and from sitting near them. In this way women will also protect their cycle. Likewise, when a woman has just given birth she should not perform Agnihotra until the bleeding has completely stopped.
Many ancient cultures knew about the impact of subtle energies on the atmosphere. Thus, many disciplines and customs which required refraining from doing certain activities at certain times were quite common. Only recently has modern science started to investigate these subtle energies. Agnihotra is the science of purification of the atmosphere, a science of subtle energies, and as such it is governed by universal laws.