Acupuncture is used to treat many conditions

It is not the first time Mrs Blair, who juggles a busy life as a top barrister, a mother of four and head of state's wife, has experimented with alternative therapies.

Three years ago she paid �239 for a crystal pendant said to counter negativity and deflect electromagnetic radiation.

And in March when she opened a drug addiction centre in Derby she agreed to have a tiny needle inserted into her ear.

Acupuncture is used to treat a variety of conditions including stress.

It has been proven to be a very effective treatment for all sorts of addiction such as alcoholism and smoking, and is widely used to control pain.

Upside-down foetus

Oran Kivity, a member of the British Acupuncture Council said ear, or auricular, acupuncture was a relatively new technique developed by a French doctor in the 1960s.

The idea is based on the fact that a person's ear looks like an upside-down foetus

Oran Kivity Acupuncturist

He said: "The idea is based on the fact that a person's ear looks like an upside-down foetus.

"For example the ear-lobe represents the head and the outer rim is the spine.

"There are zones on the ear which correspond to every part of the body."

Mr Kivity said it would be impossible to say what the prime minister's wife was receiving acupuncture for but said it could be for something very, very trivial such as a sore toe.

It is thought Mrs Blair is wearing an intradermal needle which is often used after a session of auricular acupuncture to enhance the effects of the treatment.

Pauline Ronson, of the Auricular Acupuncture Society, said: "It acts as extra stimulation. If people need extra help, say in a stressful situation, then press needles can continue treating for that.

"In Cherie Blair's case, maybe she had it put on especially for the Labour conference or maybe she has it on quite a lot of the time anyway.

"Ear acupuncture can help in many stressful situations. If someone came to me who was going through marital problems or something as stressful I would most likely put a needle on there to help in between treatments.

"That's the beauty of ear acupuncture. You can't do that with body acupuncture."

Acupuncture appears to work by releasing endorphins, the body's natural pain-killers, into the system. The Chinese, who developed the technique, say that it has an effect on the body's natural energy streams.

BBC doctor Dr Rosemary Leonard said: "Some traditional doctors would pooh-pooh acupuncture and say it is a load of rubbish.

"But I personally believe it can work for some people, and that we should keep an open mind."