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The Science Behind Red Hair: 12 Facts About Redheads You Never Knew

What about redheads is so special? Here's what the science says about these rare-haired marvels.

Redhead Woman's Eye Close Up with Blurred Hair
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How rare are redheads?

Redheads make up only about 2% of the world’s population, but they have spawned an impressive body of folklore: They’re temperamental, they’re tied to the devil, they’re witches and they turn into vampires when they die—allegedly. As far as we know, none of these tales about the rarest hair color in the world are true, but redheads certainly occupy a unique place in human history.

“Red is such an extraordinarily important color for the human species, and it does get associated with passion and fire,” says Jacky Colliss Harvey, author of Red: A History of the Redhead.

We combed through the research about this inherited trait and spoke to anthropologists and dermatologists alike about the stereotypes, myths and fascinating tidbits about redheads. Some are weird facts about the human body, while others are just plain fascinating. Here are some fiery facts about our redheaded friends.

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Cute Daughter Admiring Pregnant Mother By Father On Sofa At Home
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Non-redheads can have a redheaded child

Red hair is a recessive trait that’s inherited. That means both parents must have this gene variant in order to contribute it to their offspring. But here’s the important part: Those parents don’t necessarily have to have red hair themselves to have ginger offspring.

Parents can be carriers for recessive genes, carrying instructions for making red hair hidden in their DNA. As a result, families that haven’t had a redhead for decades may suddenly have a carrot-top baby.

Portrait of confident mature businesswoman with red hair and blue eyes
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Red hair and blue eyes are the rarest combination

The MC1R (or melanocortin 1 receptor) gene determines hair, skin and eye color. If you’re a redhead, your MC1R gene has a mutation—or possibly several. It’s why redheads are so rare. And if you have red hair and blue eyes, the rarest hair and eye color combination, the genetic stars were in alignment. According to evolutionary biology professor Mark Elgar, PhD, of the University of Melbourne, the odds of having both traits are around 0.17%—that’s about 13 million people out of the 7.6 billion on earth.

But why is this combo so rare, especially if blue eyes aren’t the rarest eye color? Many genes and gene variations play a role. But beyond that, both traits are recessive, and having two parents who can pass down two sets of recessive genes is very unlikely.

redhead boy playing with dinosaur toys on his bed in his bedroom at home, near a window
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Redheads are not going extinct

Red may be the rarest hair color in the world, but the world is big and redheads are here to stay. While they make up about 2% of the population, that means 158 million gingers are walking the earth. Fun fact: The highest concentration of redheads—at 10%—is in Ireland. But just because they are rare, doesn’t mean these genes are being diluted.

Even when you can’t see recessive characteristics, such as red hair, they’re still a part of a person’s DNA—even if the person is displaying dominant genes like brown hair and brown eyes. Which means that it’s perfectly plausible for red hair to rear its carrot top down the family line.

Dermatologist examining patient for signs of skin cancer
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Redheads have a higher risk for skin cancer

“There’s no question that red-haired individuals are at a much higher risk for skin cancer than brown-haired individuals,” confirms Gregory Papadeas, DO, a Denver-based dermatologist and past president of the Colorado Dermatologic Society. This includes melanoma, cancer that starts in the cells that produce melanin and potentially the most serious of skin cancers.

Unlike other hair colors, redheads carry two copies of the MC1R gene, which governs the production of melanin and helps determine your hair, skin and eye coloring. The MC1R gene inform the cells that create melanin to make eumelanin (usually associated with darker hair and skin) or pheomelanin (usually associated with lighter hair and fairer skin).

“Melanin works as a shock absorber, protecting you from ultraviolet light. It’s a person’s innate sunscreen,” says Papadeas. In redheads, the MC1R gene mutates and causes melanocytes to primarily make the reddish pigment pheomelanin. And because redheads have higher levels of pheomelanin, they’re more susceptible to damage from the sun.

Unrecognizable female patient in hospital gown waits for test results
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Redheads have a higher rate of gynecological cancers

According to a large review published in PLOS One in 2017, female redheads have a higher risk of gynecological cancers, such as cervical, uterine and ovarian cancer. The authors of the study speculated that the increased risk was related to being exposed to higher levels of estrogen before birth (prenatal estrogen influences not only the emergence of certain medical conditions, but also the development of certain hair and eye colors, particularly red hair).

“Estrogen creates a predisposition to certain types of cancer, and it looks like there’s a three-way relationship between being a woman, having red hair and having these diseases,” says Peter Frost, PhD., an anthropologist who studies the role of sexual selection in shaping visible human traits.

Senior red headed woman adjusting hair in bathroom
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Redheads may age faster

A 2016 study in Current Biology found that people who had two copies of the MC1R gene (which confers red hair) appeared as many as two years older than people who did not hold both copies. According to the authors, this was about the same as the effect of smoking on perceived age.

The link between red hair and aging had nothing to do with skin damage from too much sun exposure (which produces wrinkles and dark spots), as you might expect. Instead, the gene variants seemed to be connected with pathways that governed sagging skin, among other things. According to the authors, this is the first evidence of a genetic basis for perceived age. Whether or not it will lead to the fountain of youth is another question.

close up of a woman with red hair wincing in pain
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Redheads have a higher pain threshold

Several studies have found that women with red hair have a higher pain threshold. “The pain threshold is the limit from where you don’t feel anything to where you just start to feel pain,” explains David Fisher, MD, PhD, chief of dermatology at Massachusetts General Hospital, who has conducted a number of studies on red-haired individuals.

A 2021 study co-authored by Dr. Fisher sheds light on why this is. The research involved red-haired mice (which possess similar MC1R variants as humans) and indicated that the MC1R gene responsible for red hair is also involved in regulating expression of factors that govern certain pain sensations. The simple explanation is that redheads’ melanocytes (pigment-producing cells) release factors that effectively favor the signals to the brain that say “don’t feel pain” over “feel pain.” One day, he adds, these findings may lead to pain-relieving medications that are safer than those currently on the market.

Orthodontist Talking With red hair Patient About Surgery
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But redheads may require more anesthesia

While studies suggest that the general pain tolerance of redheads may be higher, it also suggests that redheads experience pain differently and may even have different pain management requirements. The link between red hair and anesthesia is still being studied, but there is both research and anecdotal evidence to support the idea that redheads require more anesthetic to be sedated.

According to a small study published in the journal Anesthesiology, women with red hair required up to 20% more anesthesia to keep them sedated than women with dark hair. This has to do with pain sensitivity and tolerance rather than pain threshold. And sensitivity may vary according to the type of pain—heat, cold, electric shocks and stinging pain—although specific findings vary from study to study. This tendency may help explain why people with red hair tend to be more afraid of the dentist and, in fact, visit the dentist less often, per a study in the Journal of the American Dental Association. (Which, of course, is not to say that other people don’t also feel anxiety faced with the prospect of pointy dental tools.)

It’s important to note that this school of thought does have its fair share of detractors, and one study from the Canadian Journal of Anesthesia found that people with red hair didn’t actually need higher doses of anesthesia. The connection is still being studied, but the bottom line is that individuals with red hair (and anyone else) who feels pain should say so, says Dr. Fisher. “That’s not hysteria,” he says.

red haired Man With Long Beard Wear Black Sporty Suit Doing Yoga Meditation outdoors on Sunny Beach
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Redheads produce more vitamin D

Vitamin D is essential for bone health and is synthesized when you’re exposed to ultraviolet B (UVB) rays from the sun. One 2020 study in Experimental Dermatology found higher levels of a precursor to vitamin D (calcidiol) in redheads, suggesting that gingers could produce more of the vitamin than people with other hair colors. The level of calcidiol also corresponded to how red the hair was.

It’s not exactly clear why this occurs, similar to why people blush. But authors speculated that people in parts of the world with low intensity UVB rays (namely central and northern parts of Europe) developed this ability to survive in areas where the sun rarely shines. According to Dr. Fisher, through evolution, the MC1R variant was advantageous to achieve healthier vitamin D production.

portrait of a redhead woman in a bar at night
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Redheads are perceived as more temperamental

Yes, there have been studies on the perceived personality and attractiveness of redheads. One group of researchers instructed the same woman to sit in different nightclubs with hair dyed either blonde, brunette or red. She was approached significantly more frequently by men in the blonde condition. Researchers then used images of the same woman, rated by 126 men. This study, published in the Scandinavian Journal of Psychology, found that the redhead was rated as the least shy, the most temperamental and the most sexually promiscuous of all hair colors. (Brunettes were considered more approachable, while blondes were perceived as more needy.)

three young redheaded brothers sitting together in a blue arm chair
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Redheads may have more children

According to a study in PLOS One co-authored by Frost, redheads may have more children, despite having more fertility problems. This could be explained by any number of factors, none of them conclusive: Redheads seem to start having children earlier in life.

Colliss Harvey, who is a redhead herself, has her own theory. “I think the association between redheaded women and sexuality came about through the fact that we can synthesize vitamin D more effectively,” she says. “Above everything else, we have a nice strong skeleton and pelvis for carrying and bearing children. It might go back to some primeval association. If males chose redheads, it increased their chances of breeding.”

Couple Coming Home After Going On Date Together
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Redheads may have more sex

Some research has shown that women with red hair are more sexually active, but experts question whether it’s due to their suitors. A 2022 study published in Frontiers in Psychology looked at 110 women (34% of whom were redheads) and found that redheaded women scored higher on measures of sexual desire and reported more sexual activity and more sexual partners. They also became sexually active earlier than people with other hair colors.

It’s not entirely clear why this is the case (similar to earworms). The authors speculate that it could be due to their partners’ more frequent attempts to initiate sex, rather than the woman’s desire. “Perhaps it’s the exotic novelty factor,” says Frost.

About the experts

  • David E. Fisher, MD, PhD, is an internationally known researcher, clinician and academic who is chief of the Massachusetts General Hospital Department of Dermatology at Harvard Medical School in Boston. He is also director of the Melanoma Center and, until recently, served as president of the Society for Melanoma Research.
  • Peter Frost received a PhD in anthropology from Université Laval in 1995. His main research interest has been the role of sexual selection in shaping visible human traits, especially skin color, hair color and eye color.
  • Jacky Colliss Harvey is the (redheaded) author of Red: A History of the Redhead, which became a New York Times bestseller. Her next nonfiction title, Noble Domes, is a cultural history of baldness, forthcoming from the University of Chicago Press.
  • Gregory Papadeas, DO, is a private-practice dermatologist in Denver. He is also a fellow of the American Academy of Dermatology and past-president of the Colorado Dermatologic Society, as well as The American Osteopathic College of Dermatology.

Sources:

Amanda Gardner
Amanda Gardner is a freelance health reporter whose stories have appeared in cnn.com, health.com, cnn.com, WebMD, HealthDay, Self Magazine, the New York Daily News, Teachers & Writers Magazine, the Foreign Service Journal, AmeriQuests (Vanderbilt University) and others. In 2009, she served as writer-in-residence at the University of Wisconsin School of Medicine and Public Health. She is also a community artist and recipient or partner in five National Endowment for the Arts grants.