How Having Red Hair Affects Your Health
by Elizabeth Howe, Writer / Editor
Disclaimer: This article was originally written in 2022 for my Medium blog. The information and research presented reflect the knowledge available at that time. While the content remains relevant, readers should note that newer studies may provide additional insights into the topics discussed here.
Red hair is a unique genetic trait, found in only about 1-2% of the global population⁹. But being a redhead involves more than just having a rare hair colour. The same gene mutation that produces red hair, located in the MC1R gene, also impacts other aspects of health. This mutation affects how the body processes sunlight, experiences pain, and responds to anesthesia.
What Causes Red Hair
Red hair is a recessive genetic trait. This means that if you have red hair, both of your parents have to have the gene for red hair in their DNA, even if they don’t have red hair themselves.
A phenotype is the observable genetic trait, such as hair colour, eye colour, or height and a genotype is the genes that cause the phenotype. For every phenotype, you have two versions of the gene (called alleles) that make up the genotype. You get one from your mother and one from your father.
Each of these alleles may be dominant or recessive. If your genotype contains at least one dominant allele, then that version of the gene will be expressed in the phenotype. For a recessive phenotype to be shown, two recessive alleles will be needed in the genotype.
This can be a little confusing if you haven’t studied biology (or even if you have!). The punnet squares in the images below may help you visualise this a little better. Obviously, there are more hair colours than red and black and this is a very simplified explanation. However, it still gives a basic understanding of how recessive and dominant alleles work.
Red hair is a recessive phenotype and black hair is dominant. This means, to have the red hair phenotype, you would need to have both recessive alleles in your genotype.
As mentioned before, you get one allele for each gene from each parent. This means that there are four possible combinations of genotypes for every phenotype (in this case — hair colour). The alleles are represented by the letter ‘H’ (for hair colour). The dominant hair colour (black) is represented by a capital H, and the recessive hair colour (red) is represented by a lowercase ‘h’.
In the first punnet square, both parents have black hair since they both have at least one dominant allele. In this case, their children have a 100% chance of having black hair as in all combinations the children have at least one dominant allele.
In the second punnet square, each parent has black hair. However, in this case, they both have one dominant and one recessive allele for hair colour. As you can see, there is one combination in this situation that would result in red hair. This means that these parents have a 75% chance of a child with black hair and a 25% chance of a child with red hair.
In the third punnet square, one parent has red hair and the other has black hair. The parent with black hair has two dominant alleles. This means that they will not have any children with red hair even though one parent does.
In the fourth punnet square, one parent has red hair and the other has black hair. However, in this case, the parent with black hair has one recessive allele. This means their children would have a 50% chance of either black or red hair.
Ok, so that was a basic overview of how our genes from our parents give us our physical traits, but what actually causes red hair?
Well, it turns out that red hair is caused by a mutation on chromosome 16 in a gene called the melanocortin 1 receptor (MC1R). This gene is responsible for producing a substance called melanin. Melanin causes the pigmentation in your skin, hair, and eyes.
However, people with the mutated MC1R gene do not produce much melanin. Instead, they produce an excess of pheomelanin. Pheomelanin is a molecule that causes the pinkish-red colour of your lips, nipples, other pinkish body parts, and red hair.
A mutation in the MC1R gene does not only cause red hair, but it can make you more susceptible to sunburn and affect how you react to anesthesia and pain.
More Susceptible to Sunburn
People with red hair tend to be more susceptible to sunburn and melanoma.
Melanocytes — skin cells with the MC1R receptor on them — release the brownish pigment melanin in response to sunlight. This helps to protect your body against damage caused by UV rays. Melanin acts as a physical barrier that scatters the UV rays and as a filter to reduce the penetration of UV rays through the skin¹. This is why you tan in the sun.
For those with red hair, the MC1R gene has a mutation. This means that the MC1R receptors on melanocytes are not ‘normal’. Because of this, they do not release very much melanin in response to UV rays. This is why many people with red hair find that they do not tan naturally but do have lots of freckles.
Unfortunately, the lack of natural tan is not the only downside of the mutated MC1R gene. Reduced melanin production leaves redheads with a much higher risk of sunburn and skin damage by UV rays. This can lead to an increased risk of developing melanoma.
If you have red hair, it is so important to take care of your skin in the sun. This includes covering up, wearing a hat, and always using sunblock (even when you think you don’t need to).
Red Hair and Anesthesia
People with red hair may require more anesthesia than others. One study from 2006 examined the general anesthetic requirement of women with red hair compared to women with dark hair². This study found that women with red hair needed 19% more desflurane than those with dark hair. This was a significant difference in the amount of general anesthetic required.
Although the mechanism behind this is not well understood, it is likely to be due to the expression of MC1R in the central nervous system (CNS). MC1R is primarily expressed in hair and skin cells. But, it is also expressed in low amounts in the CNS on cells such as glial cells, pituitary cells, and periaqueductal gray matter cells³. These areas of the CNS are associated with anesthetic reactions and pain⁴ ⁵.
Red Hair and Pain
In addition to altering the reaction to the anesthetic, a mutated MC1R gene can result in redheads having a higher pain tolerance. This is because the MC1R gene is involved in pain modulation and when mutated, it causes a distorted perception of pain⁶.
This increased pain tolerance is a result of the loss of typical MC1R function in pain perception⁷. Typically, melanocytes release a molecule called proopiomelanocortin (POMC). PMOC is then cut up to create hormones that increase the perception of pain.
However, in redheads, the mutated MC1R gene causes the cells to release less POMC than ‘normal’. This results in less of the pain-increasing hormones being created. This causes a reduced perception of pain. Additionally, the mutated MC1R gene affects MC4R proteins which increase overall pain tolerance.
Because of the changes in pain signaling due to the MC1R mutation, redheads may require lower doses of opioid pain medications⁷.
Interestingly, although redheads typically have a stronger overall tolerance to pain, it is thought that they may be more sensitive to thermal pain⁸.
Conclusion
In addition to being one of the rarest natural hair colors, the gene that causes red hair has a lot to do with other processes in the body. This affects how redheads react to sunlight, anesthesia, and pain.
People with red hair should be aware of these differences. It’s important to take care of your skin and protect it from the sun. Additionally, the increased need for anesthesia clearly becomes an issue when undergoing surgeries.
References
- Kaidbey KH, Agin PP, Sayre RM, Kligman AM. Photoprotection by melanin — a comparison of black and Caucasian skin. J Am Acad Dermatol. 1979;1(3):249–260. doi:10.1016/s0190–9622(79)70018–1
- Liem EB, Lin CM, Suleman MI, et al. Anesthetic requirement is increased in redheads. Anesthesiology. 2004;101(2):279–283. doi:10.1097/00000542–200408000–00006
- Gradwohl SC, Aranake A, Abdallah AB, et al. Intraoperative awareness risk, anesthetic sensitivity, and anesthetic management for patients with natural red hair: a matched cohort study. Can J Anaesth. 2015;62(4):345–355. doi:10.1007/s12630–014–0305–8
- Roizen MF, Newfield P, Eger EI 2nd, Hosobuchi Y, Adams JE, Lamb S. Reduced anesthetic requirement after electrical stimulation of periaqueductal gray matter. Anesthesiology. 1985;62(2):120–123. doi:10.1097/00000542–198502000–00004
- Dussor G, Boyd JT, Akopian AN. Pituitary Hormones and Orofacial Pain. Front Integr Neurosci. 2018;12:42. Published 2018 Oct 2. doi:10.3389/fnint.2018.00042
- Mogil JS, Wilson SG, Chesler EJ, et al. The melanocortin-1 receptor gene mediates female-specific mechanisms of analgesia in mice and humans. Proc Natl Acad Sci U S A. 2003;100(8):4867–4872. doi:10.1073/pnas.0730053100
- Study finds link between red hair and pain threshold. National Institutes of Health. April 20, 2021. Accessed January 27, 2023. https://www.nih.gov/news-events/nih-research-matters/study-finds-link-between-red-hair-pain-threshold
- Liem EB, Joiner TV, Tsueda K, Sessler DI. Increased sensitivity to thermal pain and reduced subcutaneous lidocaine efficacy in redheads. Anesthesiology. 2005;102(3):509–514. doi:10.1097/00000542–200503000–00006
- Cunningham AL, Jones CP, Ansell J, Barry JD. Red for danger: the effects of red hair in surgical practice. BMJ. 2010;341:c6931. Published 2010 Dec 9. doi:10.1136/bmj.c6931