The herb is ground into something a bit like green cotton wool; not quite a powder but soft and malleable, called moxa punk. It burns slowly and steadily, from one end to the other, giving out a fairly constant heat and it does so without falling apart (if it's set up right).
This dependability is what makes it so valuable for warming the skin and for invigorating acupuncture points.
Why not just warm a whole area of the body? And if you're going to warm a whole area of the body, why not just use a hot water bottle, or a warm bean-bag, or sit with your back to a fire?
Come to that, why not just have a warm bath?
If you're cold, a warm bath may be an excellent idea.
But if you're always cold, there will be various reasons for it in Chinese medicine.
For example, your system may not be producing enough yang energy, so heat isn't produced.
Or it may have enough yang energy but not enough Qi to move it around.
Or you may not have enough Blood to reach your extremities ... and so on.
(And ... are you taking enough exercise to challenge your qi; eating enough food to produce good Blood; getting enough sleep to refresh both your qi and your Blood; in fact we have a whole bunch of questions to find out why your system isn't working properly.)
In Western terms your metabolism isn't coping. In Chinese terms we might say that your system is out of balance, that your yang or qi or Blood is deficient. A proper consultation and diagnosis would identify exactly how this arose and which syndrome in Chinese medicine was appropriate for treatment.
A hot water bottle or a warm bath won't be able to treat that. They may help you feel better temporarily but not for good.
Acupuncture, or moxibustion with acupuncture, is used on specific, carefully-chosen, points that re-balance or 'correct' that syndrome.
As balance returns to your system, so should your health recover.
Here's an explanation.
Suppose your car is losing power, using too much fuel, producing black smoke from the exhaust pipe. You could strap a Rolls-Royce Olympus turbo-jet to the rear bumper, fire it up and proceed tangentially down the road outside your house and off towards Mars.
That's like heating everything up. It's great, but it doesn't last; with a normal car tankful of fuel your Olympus would burn out before you even hit your neighbour's front lawn.
You need to get your car to the repair man at the garage. What will he do? He'll make his diagnosis then get at your car's engine and tinker with it. Perhaps he finds that fuel can't move fast because your carburetor has iced up. Applying warmth to the iced part of your carburetor and tuning it up is what is needed. Do that and because everything else is OK, the car starts performing properly.
Whereas if you apply a blow-torch to everything under the bonnet you might regret it.
Or take an orchestra, in which all the players except one are on good form. That one individual is slowing everything down and the orchestra can't play fast pieces. Warming up the whole orchestra just makes everyone too hot: they start sweating, get cross, and their performances suffer.
But warm that one individual up and you make real progress.
So, if you accept these analogies, you may understand why warming specific acupuncture points, that have been found over millennia to alter the balance of the way your body works in terms of Chinese medicine, can balance your system and, if everything else is working OK, get you functioning properly.
We think moxibustion arose in Northern China, where it is colder than the South. Herbal medicine, which probably started as kitchen medicine, the kind that housewives discovered and handed down to their daughters through the generations, was then in its early stages, and mugwort might have been among herbs used or experimented with medicinally.
To warm the body, probably they tried lots of different herbs.
Who knows how they chose artemesia chinensis for moxibustion?
Why not tobacco? Here are some suggestions:
Anyway, although we know that opium was used for both medicinal and narcotic purposes from the eleventh century AD we don't think the Chinese took up smoking tobacco until the 17th century AD.
Moxa is done in many ways.
Always first, we explain how it works to the patient, answer any questions and instruct the patient to tell us if it gets too hot. Some older or very young patients don't always understand so with these we take special care. (The problem for older people is that their nerve senses are less reliable so they may burn before it feels hot.)
Once the point is chosen, the moxa punk can be shaped into a cone and placed directly on the skin over the acupuncture point.
The size of the cone can range from the size of a grain of rice up to the size of a small matchbox.
Well, of course it hurts if you let it burn your skin!
But you don't. That's why you go to an expert, your acupuncturist. The intention is to let it burn down until the hot gases warm the herb's oils which waft towards the skin making it heat up AT THAT ACUPUNCTURE POINT. Your acupuncturist will have told you what to expect and what to say so that he can remove it quickly.
He may then repeat it. With small cones of moxa he might repeat it 5, 10, 50 or more times. (With practice he gets quite good at it!) This produces a gradual and consistent glow at that one point, which can make for a powerful treatment.
Fiddling about with thousands of tiny rice cone-sized moxa punks is time consuming - and actually quite hard work. Also, because moxa punk smells, it's not always popular with the neighbours. So this isn't much done by many acupuncturists.
Larger cones obviously produce a stronger heat over a larger area. So they are not quite so specific. They are also used in some countries to produce a welt leading to a scar. For example, there are points on the back that the Chinese claim can cure asthma when scarred by moxibustion.
In the West, any kind of scar from moxa is unpopular. In China, in the past, patients were more forbearing.
Since most acupuncture points are beneath the surface of the skin, and since manipulating a needle can attract the 'qi' to the point before warming it, many acupuncturists insert and manipulate the needle first, then place moxa punk around the head of the needle before set it alight.
As the punk burns, its heat is transferred down the shaft of the needle and directly through the skin to the 'qi'.
This can make their moxibustion very effective. It is also cleaner than moxa directly on the skin.
Dangers? That the moxa punk or its ash falls and burns the skin. Acupuncturists guard against this by placing card round the base of the needles so that if ash does fall, it falls onto the card not the skin.
Specially shaped spoons are often used to remove the ash.
Moxa on needles can be repeated many times, in different needles in different places on the body. For the acupuncturist this can be like the circus act where many plates are kept revolving on long poles on stage, but with experience it's not difficult.
Resembling cigars, moxa rolls use mugwort tightly wrapped into special paper rolls. The end is set alight and waved over the acupuncture point at a distance of a centimeter or so.
It is important to keep the burning tip of the roll moving around, or over a number of adjacent points, so that it doesn't burn. Patients are usually perfectly able to report when it gets too hot.
Done correctly this is also highly beneficial and much faster than the other ways mentioned above.
Various herbs in the past were blended with the moxa punk for moxibustion in rolls, supposedly to provide other benefits. This is now increasingly frowned upon (at least in the UK) because of suspected carcinogens in the smoke.
Moxa punk is also used in enclosed boxes in which the punk is placed on a wire mesh a short distance above the skin of say the abdomen. When lit, the inside of the box heats up and the heat is conveyed through the hot gases to the skin. These boxes can get very hot, burn for ten to twenty minutes and produce strong odours and plenty of smoke. Good ventilation and forgiving neighbours are important.
One clinic I ran was in the middle of a busy office centre.
After using moxibustion I noticed girls from the adjoining offices hanging around outside my room.
Taking deep breaths they were smiling happily. They thought I was burning a herb with special properties, well-known among drug-takers: moxa can smell a bit like that. (I enjoyed their appreciative and conspiratorial looks for a while but eventually I had to disabuse them.)
And some moxa rolls do or did contain other herbs, (although not that one).
But the odour and smoke can be a problem. For the acupuncturist who uses it daily, there also is a small risk of lung damage; small but not negligible.
The odour and smoke can disturb others.
So ingenious acupuncturists have produced punk made basically of carbon powder crushed into the shapes of cones and rolls. This produces no smell and not much smoke.
However, they are harder to light and they still produce ash so nothing is perfect. The carbon also comes off onto your fingers and clothes too.
But ingenious shapes and methods of using this are on the market, some of them from Japan and Korea: the Chinese have been slower to adapt to this method.
Still, carbon rolls do the moxibustion job effectively.
You can grow it or gather it from the wayside then make it yourself.
In fact, Royston Lowe, now sadly deceased but one of the people who put acupuncture on the map in the UK and was Principal of the British Acupuncture College for many years, tried making it himself.
He collected and dried British mugwort - artemesia vulgaris.
He then removed the stalks and crushed and powdered the leaves.
Then he tried to blend it into what we know of as moxa punk.
It never quite worked as well as he had hoped. Getting the right consistency was difficult and it didn't burn steadily. It also seemed to go mouldy easily.
So don't bother to make it yourself. Buy it instead, from importers from China where they certainly do manufacture it on an industrial scale, having long since sorted out moxibustion problems.
They grow different kinds of moxa. It is cultivated, not gathered from the wild, so probably isn't organic, in the sense that fertilizers will have been used. But it is relatively cheap.
Keep it dry and it will last for ages - for years.
3000 years of Chinese being stressed, and at last, there's a book about it!
'Qi Stagnation - Signs of Stress' by the author of this website, Jonathan Clogstoun-Willmott, puts in simple English what Chinese medicine knows about Stress.
Once you get the idea, it can be a revelation. Not only does it explain what happens during stress, but it suggests what you can do to help yourself, what works, and why.
Full details? Click Qi Stagnation - Signs of Stress.