Not many people enjoy visiting the dentist but people with red hair tend to fear the dentist more than others -- and genetics could explain this, according to U.S. researchers.

A few studies in recent years have found that redheads tend to be less responsive to local pain-blockers and may need larger doses of anesthetics to get the same pain relief as people with other hair colors.

But the latest findings by U.S. researchers, published in the Journal of the American Dental Association, found redheads tend to be particularly nervous about the dentist, possibly because of the heightened fear of pain.

"They were more than twice as likely to avoid dental care," said the researchers from the Cleveland Clinic, Cleveland, Ohio, and School of Dentistry at the University of Louisville, Kentucky.

Researchers believe redheads are more sensitive to pain because of a genetic variation responsible for red hair.

The mutation in the melanocortin-1 receptor gene, or MC1R, leads to red hair and fair skin.

While it was once thought that changing the MC1R gene only affected the skin, hair and eyes, more recent research has shown that it also functions in the brain, influencing a person's sensitivity to pain.

The latest study involved testing 144 white adults for the MC1R gene variant and asking them about dental care anxiety, fear of dental pain and whether they avoid dental visits.

They found the gene variant in 65 of 67 redheads and 20 of 77 people with brown or black hair.

When the researchers analyzed the data, they found the people with the MC1R gene variant had more anxiety about the dentist and were more than twice as likely to avoid dental care.

Researcher Catherine Binkley from the University of Louisville, said this suggested that dentists should ask all patients -- but especially redheads -- about their anxiety over any procedures they must have and then use "appropriate modalities" to help them manage the problem.