Redheads might have a better excuse than the rest of us for avoiding the dentist.

For several years now scientists have known that the same genetic variations that give redheads their fiery manes can increase the amount of general or local anesthetic a person needs in order to be properly put out or numbed up.

New research suggests that the effect of these variations is strong enough, and hasn’t been addressed by dentists well enough, that the people who carry them are more than twice as likely as those who don’t to avoid going to the dentist altogether.

Researchers at the University of Kentucky surveyed 67 redheads and 77 dark haired people about their general anxiety levels, their dental treatment-related anxiety and their fear of dental pain. The results, published in the July issue of the Journal of the American Dental Association, reveal that while hair color has no effect on general anxiety, redheads are more likely to be apprehensive about sliding into the dentist’s chair.

A closer look at the data showed that increased dental-treatment anxiety and fear of dental pain is found in all people with the variants in the MC1R gene associated with red hair, even those people who carry these variations despite having dark hair.

The protein encoded by the MC1R gene is found in melanocytes, the cells that give hair and skin their color. The variants associated with red hair alter the protein’s function, tipping the balance of pigment production in melanocytes from black-brown eumelanin to red-yellow pheomelanin. Researchers don’t yet understand how this same protein impacts pain sensitivity and anesthetic needs.

People carrying one or two of the MC1R variants had 2.46 times greater odds of avoiding routine dental care compared to those who carry none. The authors speculate that this might be because prior dental experiences have left them in pain.

(23andMe customers can use the table at the end of this post to see if they carry any of the MC1R variants associated with dental treatment-related anxiety, fear of dental pain and avoidance of dental treatment.)

The researchers recommend that dentists evaluate all patients, especially those with natural red hair, for dental procedure-related anxiety and take whatever steps are necessary to help them manage their feelings and make it to their regular check-ups, because as the saying goes, “Ignore your teeth and they’ll go away.”

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In this week’s installment of “The Wild Side,” her weekly column in the New York Times, evolutionary biologist Olivia Judson explains that there are many kinds of mutations. Some affect the parts of genes that encode proteins, the molecules that do most of the work in a biological organism. By changing the structure of these functional molecules, these mutations can dramatically affect an organism’s appearance, metabolism or behavior. Mutations in the protein-coding region of the MC1R gene, for example, influence skin, hair, coat and feather color in humans, mice and birds.

Other mutations affect regions of the genome that determine where, when or how much of a protein is produced. These regulatory mutations can cause effects just as dramatic as the functional ones that alter protein structures. For example, a mutation in a genetic switch that controls the LCT gene allows many people – usually those from cultures where raw milk is a regular part of the diet – to digest the milk sugar lactose as adults. Until relatively recently in human (pre)history, that gene was always turned off after infancy. In most of the world’s people, it still is today.

It will take decades of research to understand how these regulatory mutations influence our biology; Judson guesses they play a major role in differentiating us from other species. And closer to the mission of 23andMe, they probably play a big role in differentiating us from one another as well.

So next time you hear the word “mutation,” don’t think of three-eyed fire-breathing lizard-men – think of yourself.

Illustration by Derek Grime/istockphoto.

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