By FIONA MACRAE

Last updated at 08:17 04 October 2007

Chillis could be soon hot stuff in dental surgeries and operating theatres.

The compound which gives the peppers their zing has been used to make the 'holy grail' of anaesthetics - a drug that wipes out pain without numbness and paralysis.

Such a painkiller could have a multitude of uses, from easing the trauma of childbirth, to making trips to the dentist more bearable.

It could even be used to calm the chronic itching of eczema and other skin conditions.

Scientists say the drug, which is a combination of the chilli chemical capsaicin and a compound related to the commonly-used anaesthetic lidocaine, is unique in its ability to dull pain without affecting movement or touch.

Traditional anaesthetics have a more wide-ranging effect, acting on cells involved in movement and touch as well as those that sense pain.

Dr Story Landis, of the US National Institute of Neurological Disorders and Stroke, which funded the study, said: 'The Holy Grail in pain science is to eliminate pathologic pain without impairing thinking, alertness, coordination or other vital functions of the nervous system.

'This shows that a specific combination of two molecules can block only pain-related neurons. It holds the promise of major future breakthroughs for the millions of persons who suffer with disabling pain.'

Rats given an injection of the anaesthetic were able to tolerate more heat than usual, while moving around normally, the journal Nature reports.

Researcher Professor Clifford Woolf, of Harvard Medical School and Massachusetts General Hospital in Boston in the US, said: 'We're optimistic that this method will eventually be applied to humans and change our experience during procedures ranging from knee surgery to tooth extractions.

'Eventually this method could completely transform surgical and post-surgical analgesia, allowing patients to remain fully alert without experiencing pain or paralysis.

'In fact, the possibilities seem endless. I could even imagine using this method to treat itch, as itch-sensitive neurons fall into the same group as pain-sensing ones.'

In time, it may be possible to package it in pill form, rather than giving it as an injection.

There are, however, several hurdles to be crossed before the technique can be tested on human patients.

Scientists will have to find a way of removing the temporary burning sensation associated with the use of capsaicin, as well as prolonging the pain-relieving effect of the drug.

This is not the first time that capsaicin has been shown to have promise in medicine.

The chemical, which is also found in pepper sprays used to control riots, has been shown to make cancer cells self-destruct.

Capsaicin helps prevent and heals stomach ulcers and has anti-inflammatory properties - something which could lead to new treatments for arthritis.

Chilli is also thought to speed up the metabolism, aiding weight loss, and ancient cultures used the spice as an antiseptic and to treat cholera and bronchitis.