A new study has found that redheads are more than twice as likely to avoid a visit to the dentist - possibly because they are more sensitive to pain. But does hair colour really mean more discomfort in the dentist chair?

Nicole Kidman, Hazel Blears and Prince Harry may all share ginger coloured locks, but could they also share a fear of the dentist? Some scientists say yes.

Perhaps no-one enjoys the prospect of the dentist's drill or a shot of novocaine, but new findings published in the Journal of the American Dental Association suggest that the problem may be a bit more serious for redheads.

The research, conducted by the Cleveland Clinic in Cleveland, Ohio, comes a few years after other studies found that people with red hair are typically more sensitive to pain and more resistant to anaesthesia - and require about 20% more of it to be effective.

This new study measured the anxiety that redheads feel about the dentist and concluded that they are not only nervous, but are more than twice as likely to avoid a visit altogether compared with their brunette and blonde counterparts.

The researchers recommended that dentists proceed gingerly, so to speak, by evaluating all patients - especially redheads - for anxiety.

So is it true? Some scientists aren't yet convinced, citing studies that suggest the exact opposite - maybe redheads are actually more stoic.

"Careful work has been done to suggest that redheads may well have a reduced sensitivity to pain," says Ian Jackson, head of medical and developmental genetics at the Medical Research Council in Edinburgh. "They respond to analgesics [painkillers] better than non-redheads."

Red locks are usually caused by a mutation in a gene called MC1R, which produces the substance that gives hair, skin and eyes their colour. Some studies have indicated that this mutation may also affect the way pain is felt. But scientists don't necessarily agree on how it works.

A few years ago, Canadian researcher Jeffery Mogil published findings that people with red hair may actually have a higher tolerance for pain and require less anaesthesia during surgical intervention.

And so far, Mr Jackson's research has pointed in a similar direction.

Using mice with the mutated redhead gene - which actually turns them yellow, not ginger - he found that male "redheads" had the same pain tolerance as non-redheads. And the female redhead mice actually had an increased tolerance for heat pain and a decreased tolerance for cold pain.

"You stand the mouse on iced water and you see how it moves its feet," he says of the technique.

While this study hasn't yet translated to humans, Mr Jackson says the comparison would be similar to the pain felt while washing dishes in hot water. And, according to his findings, ginger-haired women may be able to handle the higher temperatures.

So what happens when different scientists produce entirely different results? More testing, says Mr Jackson.

In the meantime, one former dentist isn't yet convinced.

"Some people are more anxious than others and it doesn't really depend on the colour of their hair," says Gordon Watkins, who practised dentistry in Norwich for more than 40 years. He is currently a member of the British Dental Association's Health and Science committee.

"I don't have any recollection of redheads who had any more pain than the rest of the population," he says.

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