Fear of the dentist may, for some, be gene-based. Redheads are more sensitive to pain, and require more numbing than blondes or dark-haired dental patients, according to the latest research published in the Journal of the American Dental Association.

Surveys of 144 people, 67 of whom were natural redheads, revealed varying levels of fear and anxiety surrounding dental visits. Researchers compared this information with blood tests for a mutation of the MC1R gene, which produces melanin, giving skin, hair, and eyes their color. In redheads, it creates freckles, fair skin, and ginger hair. Researchers believe it also makes people more resistant to certain pain medications. All but two of the redheads in the study tested positive for the gene.

Earlier research has shown that men and women with red hair were twice as likely to avoid dental care as people with dark hair. Redheads were also found to require 20 percent more general anesthesia than blondes and brunettes.

Redheads “require more generalized anesthesia, localized anesthesia,” said Dr. Daniel Sessler, author of an earlier study and Outcomes Research Department chair at the Cleveland Clinic in Ohio. “The conventional doses fail. They have bad experiences at the dentist and because of the bad experiences, they could avoid dental care.”