Introduction to moxibustion
In a primitive society, the discovery and use of fire improved the conditions of living and raised the chances of survival and reproduction of the specie.
When getting warm near a fire, some cold and pain in the joints and diseases of various parts of the body were relieved or disappeared; so it was found that the scorching, fumigating and roasting can treat diseases,It is likely to be the origin of the moxibustion technique.    “Jiu” means “scorching” as well as fumigating and roasting. The character “Jiu” denotes the persistent fumigating and roasting.    The earliest “Jiu” (moxibustion) refers to fumigating and roasting with bright fire with the branches of a tree or firewood as the moxibustion materials.
Later, it was found that moxa floss is warm in nature and is easy to be ignited, persistent in burning and strong in penetration and has no bright fire, and cannot scorch the skin. Thus it was used as the main moxibustion materials.The moxibustion technique was also called “attack” method and “fire” method in ancient times. Moxibustion is the burning of mugwort over inflamed and affected areas of the body.
The mugwort comes in sticks that closely resemble the circumference and length of a cigar. Moxa cones can also be burned. The mugwort, called Ai Ye in traditional Chinese medicine, is positioned over acupuncture points to stimulate the qi and blood.
Artemisia vulgaris is a species of chrysanthemum.
“The moxa leaf is bitter and acrid, producing warmth when used in small amount and strong heat when used in large amount.
It is of pure yang nature, having the ability to restore the primary yang from collapse.
It can open the 12 regular meridians, traveling through the three yin meridians to regulate qi and blood, expel cold and dampness, warm the uterus, stop bleeding, warm the spleen and stomach to remove stagnation, regulate menstruation, and ease the fetus....When burned, it penetrates all the meridians eliminating hundreds of diseases.”
Yang can be activated by the Artemisia leaf for its warm nature.
The acrid odor of the leaf can travel through the meridians, regulate qi and blood, and expel cold from the meridians, and its bitter nature resolves dampness; it is used as a necessary material in moxibustion treatment.
4) To prevent diseases and keep healthy.
It is often said:
“If one wants to be healthy, you should often have moxibustion over the point zusanli [ST-36].”
In Notes on Bian Que’s Moxibustion, it says, When a healthy man often has moxibustion to the points guangyuan [KI-4], qihai [KI-6], mingmen [GV-4], and zhongwan [KI-12], he would live a very long life, at least one hundred years.”
The relationship of moxibustion to the herbal material used for moxa wool depends on the technique.
For example, when moxa cones are burned on the end of acupuncture needles, the constituents of the moxa do not interact with the skin and the local effect is that of transferring heat to the acupoint.

When a moxa pole is used, there is some transfer of active constituents to the skin, but not much; the effect is still mostly heat, but to a broader area.
When the moxa cone is burned directly on the skin, active constituents are transferred to the skin.
This latter method was the most commonly used traditional approach, as best as one can tell from the old literature.

When moxa is burned on top of another herbal material, such as a slice of ginger or garlic, cake of aconite, or mound of salt or powder of herbs in the navel, the heat will drive some of the ingredients of the interposing herbal material into the skin, but little of the moxa wool ingredients will penetrate.

Fresh ginger, one of the commonly used interposing materials, contains compounds similar to borneol and camphor (small holes in the slice of ginger or slice of garlic permit a little of the moxa vapors to penetrate).
Of course, with all moxibustion techniques, the smoke and vapors from the moxa are ultimately inhaled.
The modern smokeless moxa poles are intended to eliminate this otherwise sure route to getting moxa ingredients internally, and might defeat part of the therapeutic action.
The Chinese technique of applying moxibustion for an extended period of time (up to 30 minutes for a treatment session), assures that the patient inhales a substantial amount of the vapors and smoke.
Artemisia leaf is also selected for its ability to burn slowly and project heat through the wool in a gentle manner.
But the important thing to note in this context is that this description is not a simple depiction of applying heat: it must be understood that some of the mugwort vapors and smoke have their effect by entering the body, either through the skin where the moxa is burned or through breathing the fumes, or both.
Moxibustion is an important and perhaps underutilized therapeutic method in traditional Chinese medicine.
It may be used alone or in combination with other modalities, such as acupuncture....This method involves the burning of moxa on or above the skin at the location of specific acupoints, or on or near the lesion itself.
The heat of the cauterization, as well as the properties of the moxa itself, serve to warm the qi and blood in the channels, expel cold and dampness, restore yang, and, in general, help to regulate the organs and restore health.the

Functions of moxibustion: it is used:

1) To warm meridians and expel cold.
Abnormal flow of qi and blood in the body usually results from cold and heat. Cold causes obstructed flow or even stagnation of qi, and heat results in rapid flow of qi.
Normal heat activates blood circulation and cold impedes its smooth flow. Since stagnation of qi and blood is often relieved by warming up the qi, moxibustion is the right way to generate the smooth flow of qi with the help of the ignited moxa wool. “If stagnation of blood in the vessels cannot be treated by warming up with moxibustion, it cannot be treated by acupuncture; blood stagnation caused by cold, should be dispersed by moxibustion.”
2) To induce the smooth flow of qi and blood. Another function of moxibustion is to induce qi and blood to flow upward or downward.
3) To strengthen yang from collapse. Yang qi is the foundation of the human body. If it is in a sufficient condition, a man lives a long life; if it is lost, death occurs. Yang disorder is due to excess of yin, leading to cold, deficiency, and exhaustion of the primary qi, characterized by a fatal pulse. At this moment, moxibustion applied can reinforce yang qi and prevent collapse. In Chapter 73 of Miraculous Pivot it says, “Deficiency of both yin and yang should be treated by moxibustion.”
Moxibustion may have more or less the same efficacy as acupuncture. People who suffer from constant circulation or "cold feeling" in the hands and feet can greatly benefit from moxibustion. It is often as effective for internal chronic ailments as acupuncture.